[Stooky Bill]

My understanding of the technical side of things is zero.

Will whatever is being done to create enough extra splits for full BBC One HD regionality be something that ITV1 HD can inherently then take advantage of, so that we *finally* stop getting Central West HD across both halves of the West Country?

It should be. There's two seperate things - making seperate versions of PSB3 - that's done by the BBC. Then there's sending those different versions to different sets of transmitters - that's Arqiva's bit.

Each version of PSB3 needs each of its services encoded and multiplexed together,so doing that for 17 regions requires 17 times the number of services on it (currently 8?)  so to cover that many regions meant a big increase in the amount of kit needed at a big cost. Bear in mind that everything is resilient, so there's two of everything

My understanding is that part of the issue was who would pay for the new infrastructure - if ITV wanted to expand to full regionalisation then they'd pay and the BBC and Ch4 would be able to use it too. 

Not sure what has changed now in terms of the political side of things, but the system that did PSB3 has been replaced by a brand new one that is more efficient, does things differently and is easier to scale. Therefore they now have the capacity to do lots of variants, and also can squeeze more in, hence the addition of BBC4 HD last year. 

I've no idea how much needs changing in Arqivaland to enable this, but my understanding is that their distribution network is fairly flexible in terms of sending signals from their customers to the relevant transmitters

So I think that both ITV and Channel 4 will be fully regional soon, after all they have more of an incentive than the BBC - they aren't showing the right ads to the right viewers on HD DTT