I once had to create an airport for a client under this specific provision, he absolutely insisted on perimeter patrol vehicles. Since it was a private job, I'd had the freedom of modifying global attributes, it would be run in a dedicated system. However, I had to retain default highway traffic, so Federico's restriction prevailed. I even explored modifying airport vehicles, but found there was no way to establish, or ensure schedules. Finally, I followed someone else's advice and created another airport within my airport. The "security office" became the main apron, the impossibly small runway was inside the security office and the flightless vehicles had to navigate a taxiway that circled the airfield, before finally timing out parked in front of the office in abject frustration. I was dreadfully afraid some jumbo jet would spawn in the security office parking lot before the guy paid me, but apparently I covered that provision too. If you designate the parking "military,"only military planes will spawn there and since they are camouflaged, I never see them anyway.
Actually you can just remove them from your hangar, or reconfigure planes to not have an AI version, but food for thought, just the same.