Depends how the OLE supply is fed to PRDC, all units appear to be pan down so it may just be a working at height concern.
Yeah probably, perhaps also the fact that the OLE is just in the way even if it is off.
There was actually a Track Sectioning Location (TSL) substation installed when PRDC was built called "Harlesden" located around "Railnet Junction", I'd imagine this allows the terminal to be fed from it's own circuit breaker(s) being electrically separate from the High Level Goods line or the Up and Dn Carriage Lines - though I can't be certain myself.
But even apart from that, you can see in the picture posted above that each of the terminal roads has an OLE switch installed that also could be used. I'd be surprised if further switches don't exist on the four Railnet departure roads that could allow them to be sectioned off to act as earthing points for the required hazard protection.