[Stooky Bill]

That's Arqiva's backup distribution for DTT - it's not a 'DSAT' service. It's been carrying the NE version of SD since Bilsdale had its fire to provide a feed to some relays

Presumably the HD version of BBC One will also carry the NE version once the HD regions rolls out on terrestrial in the coming weeks.

Once Bilsdale is back to full effect I'd have thought it will go back to being a generic non  regional BBC1, with either the News Channel or London in the opt out times

How does the satellite feed of BBC One NE&C get to air on the affected Bilsdale relays?

Do they really each have the means of inserting it into PSB1? I thought this was a fairly complex and expensive process, hence why the regional versions of PSB3 can’t just have the regional HD channels added in at the TX sites.

Or does BBC One NE&C have its own single-channel mux at these sites?

The satellite feed supplies the whole MUX (both PSB1 and PSB3 in this case) it's used as a back up for when a transmitter or relay loses its normal feed(s). Which in this case some have, so they're taking everything from satellite 

The usual default is to have a non regional version of BBC One for England, but because this is a long term outage they've swapped that out for the NE version. 

The disadvantage with this of course is that if the system is used by any other transmitter in England viewers there will see Look North. However its not that often it been used in anger and when it does its usually for a brief period