It's like the T-Mobile/Orange setup here in the UK. They have merged into EE which is the only 4G provider in the UK right now - the problem is 4G is only set up in certain cities, so I can use 4G in Edinburgh and Glasgow, and for major bits of the route home, but the gaps have almost no connectivity, and I'm back to 3G by 400 yards from my house.

Which is a pity, as 4G is 5 times faster than my home broadband :-/