Here is more evidence they pulled the teams out waiting for a normal collapse from fire...
"The most important operational decision to be made that afternoon was the collapse (Of the WTC towers) had damaged 7 World Trade Center, which is about a 50 story building, at Vesey between West Broadway and Washington Street. It had very heavy fire on many floors and I ordered the evacuation of an area sufficient around to protect our members, so we had to give up some rescue operations that were going on at the time and back the people away far enough so that if 7 World Trade did collapse, we [wouldn't] lose any more people. We continued to operate on what we could from that distance and approximately an hour and a half after that order was [given], at 5:30 in the afternoon, World Trade Center collapsed completely" - Daniel Nigro, Chief of Department
http://www.nytimes.com/packages/html/nyregion/20050812_WTC_GRAPHIC/
Nigro_Daniel.txt
"Early on, there was concern that 7 World Trade Center might have been both impacted by the collapsing tower and had several fires in it and there was a concern that it might collapse. So we instructed that a collapse area -- (Q. A collapse zone?) -- Yeah -- be set up and maintained so that when the expected collapse of 7 happened, we wouldn't have people working in it. There was considerable discussion with Con Ed regarding the substation in that building and the feeders and the oil coolants and so on. And their concern was of the type of fire we might have when it collapsed." - Chief Cruthers
http://www.nytimes.com/packages/html/nyregion/20050812_WTC_GRAPHIC
/Cruthers.txt
"Then we found out, I guess around 3:00 [o'clock], that they thought 7 was going to collapse. So, of course, [we've] got guys all in this pile over here and the main concern was get everybody out, and I guess it took us over an hour and a half, two hours to get everybody out of there. (Q. Initially when you were there, you had said you heard a few Maydays?) Oh, yes. We had Maydays like crazy.... The heat must have been tremendous. There was so much [expletive] fire there. This whole pile was burning like crazy. Just the heat and the smoke from all the other buildings on fire, you [couldn't] see anything. So it took us a while and we ended up backing everybody out, and [that's] when 7 collapsed.... Basically, we fell back for 7 to collapse, and then we waited a while and it got a lot more organized, I would guess." - Lieutenant William Ryan
http://www.nytimes.com/packages/html/nyregion/20050812_WTC_GRAPHIC
/Ryan_William.txt
"Firehouse: Did that chief give an assignment to go to building 7?
Boyle: He gave out an assignment. I didn’t know exactly what it was,but he told the chief that we were heading down to the site.
Firehouse: How many companies?
Boyle: There were four engines and at least three trucks. So we’re heading east on Vesey, we couldn’t see much past Broadway. We couldn’t see Church Street. We couldn’t see what was down there. It was really smoky and dusty."
"A little north of Vesey I said, we’ll go down, let’s see what’s going on. A couple of the other officers and I were going to see what was going on. We were told to go to Greenwich and Vesey and see what’s going on. So we go there and on the north and east side of 7 it didn’t look like there was any damage at all, but then you looked on the south side of 7 there had to be a hole 20 stories tall in the building, with fire on several floors. Debris was falling down on the building and it didn’t look good.
But they had a hoseline operating. Like I said, it was hitting the sidewalk across the street, but eventually they pulled back too. Then we received an order from Fellini, we’re going to make a move on 7. That was the first time really my stomach tightened up because the building didn’t look good. I was figuring probably the standpipe systems were shot. There was no hydrant pressure. I wasn’t really keen on the idea. Then this other officer I’m standing next to said, that building doesn’t look straight. So I’m standing there. I’m looking at the building. It didn’t look right, but, well, we’ll go in, we’ll see.
So we gathered up rollups and most of us had masks at that time. We headed toward 7. And just around we were about a hundred yards away and Butch Brandies came running up. He said forget it, nobody’s going into 7, there’s creaking, there are noises coming out of there, so we just stopped. And probably about 10 minutes after that, Visconti, he was on West Street, and I guess he had another report of further damage either in some basements and things like that, so Visconti said nobody goes into 7, so that was the final thing and that was abandoned.
Firehouse: When you looked at the south side, how close were you to the base of that side?
Boyle: I was standing right next to the building, probably right next to it.
Firehouse: When you had fire on the 20 floors, was it in one window or many?
Boyle: There was a huge gaping hole and it was scattered throughout there. It was a huge hole. I would say it was probably about a third of it, right in the middle of it. And so after Visconti came down and said nobody goes in 7, we said all right, we’ll head back to the command post. We lost touch with him. I never saw him again that day.
http://www.firehouse.com/terrorist/911/mag...e/gz/boyle.html This proves there was a big hole on the south side of the building. From the photographic evidence and these quotes which aren't meant to be technical, I suspect there was a large hole in the center of the building which may have gone up 10 stories connected to a large rip on the left side of the building which continued up another 10 or more stories. Together they would make "a hole 20 stories tall".
Hayden: Yeah. There was enough there and we were marking off. There were a lot of damaged apparatus there that were covered. We tried to get searches in those areas. By now, this is going on into the afternoon, and we were concerned about additional collapse, not only of the Marriott, because there was a good portion of the Marriott still standing, but also we were pretty sure that 7 World Trade Center would collapse. Early on, we saw a bulge in the southwest corner between floors 10 and 13, and we had put a transit on that and we were pretty sure she was going to collapse. You actually could see there was a visible bulge, it ran up about three floors. It came down about 5 o’clock in the afternoon, but by about 2 o’clock in the afternoon we realized this thing was going to collapse.
Firehouse: Was there heavy fire in there right away?
Hayden: No, not right away, and that’s probably why it stood for so long because it took a while for that fire to develop. It was a heavy body of fire in there and then we didn’t make any attempt to fight it. That was just one of those wars we were just going to lose. We were concerned about the collapse of a 47-story building there. We were worried about additional collapse there of what was remaining standing of the towers and the Marriott, so we started pulling the people back after a couple of hours of surface removal and searches along the surface of the debris. We started to pull guys back because we were concerned for their safety.
Firehouse: Chief Nigro said they made a collapse zone and wanted everybody away from number 7— did you have to get all of those people out?
Hayden: Yeah, we had to pull everybody back. It was very difficult. We had to be very forceful in getting the guys out. They didn’t want to come out. There were guys going into areas that I wasn’t even really comfortable with, because of the possibility of secondary collapses. We didn’t know how stable any of this area was. We pulled everybody back probably by 3 or 3:30 in the afternoon. We said, this building is going to come down, get back. It came down about 5 o’clock or so, but we had everybody backed away by then. At that point in time, it seemed like a somewhat smaller event, but under any normal circumstances, that’s a major event, a 47-story building collapsing. It seemed like a firecracker after the other ones came down, but I mean that’s a big building, and when it came down, it was quite an event. But having gone through the other two, it didn’t seem so bad. But that’s what we were concerned about. We had said to the guys, we lost as many as 300 guys. We didn’t want to lose any more people that day. And when those numbers start to set in among everybody… My feeling early on was we weren’t going to find any survivors. You either made it out or you didn’t make it out. It was a cataclysmic event. The idea of somebody living in that thing to me would have been only short of a miracle. This thing became geographically sectored because of the collapse. I was at West and Liberty. I couldn’t go further north on West Street. And I couldn’t go further east on Liberty because of the collapse of the south tower, so physically we were boxed in.
http://www.firehouse.com/terrorist/911/mag.../gz/hayden.html