Nah I don't believe it can ever happen like that.
http://www.youtube.com/watch?v=GApCMW1F7a0
The sequence from 10:10 to 13:24 is not how the game plays. It's full of scripting to make the AI seem absolutely perfect, and there are plenty of little things that I've never seen or heard in the game (and I just played that section for the fourth time, trying various things out).
10:23 Running away saying 'he's got a gun'
10:30 'How many are there?'
10:39 'He's right by the door'
10:48 Guy surprise attack from the side, holding Joel for another enemy to shoot, 'hold him still!'
11:53 Ellie saying 'Joel over there' with perfect timing.
12:12 Chasing down the last guy, lots of incidental dialogue from Joel. (did get 'where the fuck are you' from Joel
13:12 Joel calling for Ellie and her turning up, and perfectly reacting to the final body on the floor.
Some of these things I may have just not seen in my playthroughs, but others are just too seamless and I believe were made and scripted specifically for this demo.