Most likely a diesel power cart would be used in that scenario, but I do wonder about the operational procedures needed with ground staff working behind running power plants and main gear
No different to a current ASU start protocol. They dont work behind any running plant.
If connection is on LHS (as in this case) then the connection (pneumo or elec) is made, chocks (Nose and LHS) remain in.
Ground crew withdraw
No2 engine (i.e. RHS) is started,
Crew move back in to remove connections and chocks
Aircraft pushed back
Other engine(s) started by cross-bleed (or using elec from the No2 generators in this case).
The crew aren't working behind any running plant but on the opposite side of the aircraft body.