Re: Why oh why etc.
Surely it's time for the UK to have a Mobile "Transco/Network Rail" that owns all the infrastructure and data and the "carriers" could just be billing agents?
Do you really think the energy or rail markets are a model for mobile phones to follow? And if the carriers were reduced to mere billing agents with minimal ownership of the cost build, and no operational control or influence over assets, why bother having that pretend level of competition on the final 10% of the value chain? I work for an energy supplier, and I can assure you that the idea of splitting up the value chain in utilities has had a few modest benefits, but nowhere near enough to justify the idea.
The other flaw in your suggestion is to believe that a single network operator who took over the hugely overlapping assets of the existing MNOs would do a good job. In the electricity and gas markets this hasn't been a ringing success (and you should note that Transco has long been broken up into separate networks owned and operated by four different companies). Anyway, heard of Openreach? Suitably monopolistic, but not exactly a paragon of customer service and providing a great broadband service, is it?
Even if a single asset provider merged the assets, they'd set to to reduce the duplication, and they'd be most unlikely to build out the network where there's no coverage. Serving mobile signals to sheep will continue to have a zero profit potential, so it won't happen unless a board director happens to be inconvenienced.