In West Bengal, the main two gateway railway station - Sealdah and Howrah both have free WiFi offerings. Howrah got the first with MTS, while Sealdah got its later, but from Google-Railwire initiative.
While MTS offers 30 minutes free usage at Howrah railway station, Google-Railwire offers unlimited usage at Sealdah (though speed goes down after sometime as a part of fair usage policy).
Note that RailTel Corp (RCIL) signed an agreement with Mahataa Information India Pvt Ltd (MIIPL), an arm of Google Inc, to equip 400 stations with Wi-Fi. Hence when you are online, your ISP will not be detected as RailTel or RailWire, rather it will be detected as Mahataa Information India.
Logging in to Google's free Wifi at Sealdah Station is easy. Just keep your WiFi on your smartphone, it will be detected as RailWire WiFi.