We (the ground handler) cannot move a plane without starting the APU, if it is inop we have to call the engineers and they come out and work their magic, to be honest i think that as long as there is enough pressure in the accumulator (3000psi) they can monitor that and watch for the tug disappearing into the distance, but the insurers will not let us do that. I believe airport ops insist that an aircraft that has no power (APU inop) must have an airfield ranger escort tho what they are going to do if things go the shape of a pear is unknown