If VM wanted to it shouldn't be too difficult for them to provide a circuit from BBC Salford to the local head end and have it fed with the output of the local opt switch? (Technically rather than BBC politically, anyway)
I can see several issues with that. Firstly do VM have local head ends?
Secondly every BBC service goes through a central location before being handed over or sent out for distribution. They can switch between paths if there's an issue or substitute another region if one is out of action. Bypassing that removes that resiliance and control - they could end up with Virgin carrying something that other platforms aren't.
Plus, what feed would BBC NW opt out of ?
If they use the BBC 1HD England feed, (assuming it was made available), that has the red screen of death during opts, no good for fallback. Also their output would need to be down converted to feed the SD platforms, not part of BBC ER architecture.
There seems to be rather a lot of wishful thinking going on, when my suspicion is it'll be nothing more than BBC NW SD in an MPEG4 HD 'wrapper'