You should take a look at the new interviews too. I was reading through one and Richard Ham announced that you cannot leave the game idle anymore and let the bot take over because they weren't quite sure how to do that.
Makes me wonder how Valve was able to do that for L4D and L4D2.
The AI survivors did nothing more than follow the player and shoot zombies. Sure, they did that with fair excellance, but that was all they were meant to do.
Brink's AI's have to attack objectives which are always changing, protect teammates, shoot enemies, avoid bullets, use cover / tools - My point being Brink's AI is probably more advanced and you can't just plop it anywhere.