Hi LG, i've had the same issue. The humvee's blocking the exit after its trigger.
However, when i select the humvee and set its speed from 0 to 11 on the F10 Map during the mission, the vehicles move to their designated point. I think it has to do with the speed setting after the these humvee's are activated (trigger) >> from wp 0 to wp 1 >> speed 11 and not 0.
Then the humvee will move when activated / triggered.
Temporary solution : Taxi on to the runway and hold, and then go to the F10 Map. Select the humvees holding before your team and set its speed to 11, then they will start moving. It will only take a minute to do it.
Kind regards,
RWC.
See above
RWC's post in Mission 8: The Oil Business part 2 bugged was marked as the answer