I am willing to bet it is something very trivial like Raspberry PIs connected to dongles.

If you look at the map a lot of the locations are very concentrated; this is likely because there are shit tonne of "Chai Wallah" places in India :). However, looking at the outliers, I am not expecting a device that is creating something similar to a net nor a wifi extender.

It would be way cheaper than having some other sort of a receiver.