If you transfer a combat vehicle to an AI player, some sort of primitive AI kicks in and sends that vehicle off to attack enemies.
Sample code:
Player[1].GoAI();
Unit Unit1;
TethysGame::CreateUnit(Unit1, mapCommandCenter, LOCATION(60, 30), 0, mapNone, 0);
TethysGame::CreateUnit(Unit1, mapLynx, LOCATION(40, 5), 6, mapRPG, 0);
Unit1.DoSetLights(1);
Unit1.DoTransfer(1);
It doesn't matter where you create the units, of course, though you should try to keep some distance between the AI unit and the target so you can see what I mean.
If you transfer a non-combat vehicle (well, to be fair, I only tried Cargo Trucks) it just kinda moves off to a (seemingly) random place on the map (though it was always around the same area). Transferring structures seemed to have no effect.
Could this be anything significant? A hint of an actual AI that Dynamix may have been working on? Probably not, I just thought it was interesting and worth mentioning.