At various points over the last couple of years, I've heard WiMAX advocates talk enthusiastically about the possibility of using their favourite technology as a cheap & effective way of improving mobile backhaul.
So what's happened? As far as I can see, the need for faster, cheaper, better (ideally non-line of sight) backhaul has grown tremendously. The demand certainly seems to be there.
And a never-ending stream of alternative approaches is appearing, from fibre & metro-ethernet connections, to various forms of multiplexing & compression, even industrial-grade DSL backhaul.
But speaking to one of the largest WiMAX equipment vendors last week, I got the distinct impression that this is one of the "use cases" that hasn't made it as far as the initial marketing pitch for the technology. I suspect this is partly down to the limitations of existing interfaces (and physical space) at cell sites. But it also seems to be a distinct aversion in many traditional mobile carriers to the idea of deploying another wireless network, especially just for "spot" solutions.