I noticed this when creating an ingame mission in Altis through Eden Editor. I have a civilian trigger at a base I made in Altis and I set the trigger to activate and end the mission whenever a civilian enters the trigger circle/square. However I noticed that the trigger activates even when there aren't any BLUFOR units in the circle. It turns out that having an empty vehicle inside the civilian trigger ends the mission even if there aren't any civilians inside the trigger.
EDIT: It turns that it's not just empty vehicles but even full vehicles with people in it. As long as the vehicle is in the trigger, the trigger activates, even if the unit inside the vehicle are BLUFOR/OPFOR/INDEPENDENT