From talking with those who are working for them as PSD, they are contractually obligated by the DOS to run high profile convoys, their is a bubble around the convoy that if penetrated and time allows they first try signaling the vehicle to back off via flares or by throwing water bottles, they have signs an strobe lights on the trail vehicle telling drivers to stay back. If the drivers don't comply or there is not time to signal they fire on the car. If they are attacked they respond. In short they are not used in offensive operations. You keep trying to paint this picture that they are out there guns a blazing looking for bad guys. If they had their way they would be running low profile convoys to avoid trouble. They get paid the same whether they get shot at or not.