hello folks,
i'm lucky to work at an airport as a pushbackdriver, so i have some experience.
First of all, the panel for pneumatic panel is right on the fuselage about few feets next to the engine,
and you have a safety distance to the engine about 23 feet.
So that's the only way it works
you cannot start Nr. 2 engine, because it would suck your equipment.
and pilots are only allowed to start the sec. one after PB is completed, because they have to rise the power on running engine