Also no idea in India but in the US a lot of times although their are existing power poles internet providers can't necessarily get permission to string their fiber on them. Same problem can happen with existing in ground pipes. And any trenching or installing new poles becomes very expense.
The other issue is "long fat pipes." TCP is better tuned for it on machines now than it used to be but when you go over a long distance, the latency can decrease the usable bandwidth significantly. Of course, this seems to be more focused on last mile rather than back-haul. There are very few applications where a several nanosecond latency decrease matters.
An alternative way to imagine networking an area is running fiber into the area then having a mesh network assemble itself building to building in town/city whatever. This has the added advantage of greatly reducing the power costs of the overall network for local communications.