Ok. Here's the answer:
Building models in ofp shall have a LOD defining the available house positions for the AI. If such hasn't been defined (like the Resistance Hold Factory), then forget it: You won't get the AI acting normaly inside it...
Now, for the defined ones you can place a waypoint over, and then configure that waypoint in the "House position" field. If you don't want Waypoints, then use the following command sequence, for example:
_house = object 12223
_pos = _house BuildingPos 2
_AIUnit move _pos
The variable "_house" is just a reference from mine. You can get a map house var with the "object ID" or you can place your own house in the map and name it...
The command "_house BuildingPos _num" returns the house's _num position. notice that the City Hall has 27 positions!
The command "Move" is well known. The returned house position will - in association with the Move or DoMove - make the AI go to the pretended point.
CU.
#Edit
If you want your units to follow you inside the house, that will be more complicated...
You'll have to make a script which scans the player's position, checks which house position is nearer and then force the AI (doMove) to go there. Of course, the player will notice that his units are being ordered (silently) to go there ("Move") and he might (and surely will) abort the operation... Therefore, don't think about it. Or you can join me to make a group management script (leave the old 12 units limit within groups)... ;D