1. Place multiple enemy AI and put waypoints onto enterable building positions (1,2,3,4,etc).
2. Create a player on neutral faction (or opposing really, they'll mostly be facing walls, so you can just shoot them in the back), and check to see which direction the AI are facing.
3. Using an opposing faction player character, go around shooting the AI in the back. In none of my tests did the AI change their facing to respond to their friends being shot nearby. I used semi-auto, auto, 40mm rifle grenades, hand grenades and placed C4 charges to attempt to cause enough noise (and gratuitous carnage) to get the AI to change their facing; they didn't.
Again, for the most part the only AI that face a tactically relevant direction are the ones who's path through the building just happen to face them in a useful direction.