The thing is though, on a Voyager, the guard gives the signal to the driver to close the doors other than their own, and will then check the doors are closed and nothing is trapped before closing their own door with the key and giving the starting signal. At that point without a driver-guard buzzer it doesn't matter who controls the doors as the guard has no way of signalling to the driver. The same therefore applies to any situation where the guard dispatches from a position without an opening window. I would presume the situation would be to use the only opening windows or doors available. For most units thats the rear cab window, for 22Xs its the rear cab door, for Mk4s they would have to dispatch from the DVT.