I think I worded that wrong,what I was trying to ask was if I could up the vehicle parking spot similar to the gate parking spot by assigning codes to them, for example if I place a vehicle parking spot at terminal 4 at LAX which is American Airlines would putting the American code AAL in that vehicle spot would only American Airlines Service vehicle use that parking spot? Same with Delta at T5 and United at T7?
Maybe you haven't fully understood what I said: vehicles should NORMALLY come from a parking of the "Vehicle" type , if there is at least one, airplane parking spot won't be used, and this is of course correct. The use of airplane parking is used only as a backup strategy, if the scenery developer hasn't placed any proper vehicle parking spot.
In addition to that, the only vehicles that come and go to a parking (and again, this will be of the Vehicle type as a first choice, so it won't have any airline codes), are the Catering and the Fuel truck (which will instead use a parking of the "Fuel" type, as a first choice). All the other GSX vehicles are related to YOUR parking, so they are ALREADY related to the atc_parking_codes of the parking.