Hello,
There was a deal on 2016 between Government of India and google inc. to make available of free wifi in 500 majour railway station. It was the initiative by PM of india under Digital India programme. According to the deal google will provide only wifi access point and required hardware in specified stations and Indian government will provide internet via FOC. All FOC were/are available already under the ground. The main question here is that why google has provided hardwares in 500 stations, what is profit behind it? however approx 300 stations has been installed already and are available for access 400 station will be covered by end of 2018.

Why google providing free internet?

As per my own experience, i used twice or thrice of free wifi in railway station. My mobile number was the password to access the free wifi but just after login i saw lots of advertisement of hotels and restaurant on the page. I thought it is the reason google is providing free access points in railway stations. However speed was average due to heavy traffic.
Hope apart from me there are lots of Indian users here has tested its free wifi internet.

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Thanks
@face2face