Whilst I don't have Arma2 yet, this should still work (place it in an .sqf file and call that file from init.sqf):
Code:
if(!isServer) exitWith {};
while {alive myVehicle} do {
"respawn_west" setMarkerPos getPos myVehicle;
};
deleteMarker "respawn_west";
Obviously, replace "myVehicle" with the name of the vehicle you want them to spawn at, and ensure you have placed a marker called "respawn_west" in the editor.
I don't know how they will spawn in Arma2, but they guys should spawn next to the vehicle. If they don't, you'll have to add some metric to ensure they spawn next to it, instead.