... became part of National Grid and run the transmission networks. Thats the EHT stuff, or the big gas pipes.
In the liberalised market, the distribution networks are quite seperate, and though any of the parties might have a metering business, these have to be ring fenced and this is enforced quite stringently.
There are lots of distribution networks, and we've seen regionally specced metering before (pre-payment was only very recently unified) so it makes sense that it's BG (by far the biggest supplier) who pushes the smart metering standard.
To be honest, it's a good move by them to make it an open standard so that other suppliers can make sure they are compatible. BG are dominant enough in the market that they could have made it more difficult for the other players to enter this area so easily.
However, make no mistake about it, energy that is metered through the smart network is going to cost you more, cause the additional infrastructure costs will need to be recovered - from the end consumer.
And it's dubious as to how much of an overall energy saving there will be, cause consumers tend to have a lot of inertia. Still, it's a start...