1. a) Chosse as side "Empty". All vehicles on that side are empty and Neutral to both sides. This is also where you can find objects, such as tents, fences and more.
b) Use the "Get Out" waypoint on the vehicle. The AI inside the vehicle will disembark and move to the waypoint. However, if an enemy units detects this vehicle, it will open fire onto it because it is not on the "empty" side.
2. If your vehicle is assigned to some other unit (in the same group), it will move into formation with that unit. Check if there is a line connection the vehicle with some other unit. Then the units will be in the same group. Select F2 and click on your vehicle, then draw the line on some empty space on the map. This will "ungroup" your vehicle. It should stay right there where you place it.