In Kolkata all operators commercially rolled out 3G services. It is expected Airtel will enter into spectrum shareing & roaming agreement with Vodafone to offer 3G services in Kolkata. Idea Cellular already promised to give a nation-wide 3G roaming, and thus 3G services on pan India basis.
BSNL 3G Coverage (speed upto 3.6/7.2Mbps)
On April 2010 BSNL 3G was present over 44 cities of WB. Source Telecomtalk
Durgapur, Haldia, Behrampur, Asansol, Burdwan, Midnapur, Krishnagar, Diamond Harbour, Basirhat, Bangaon, Contai, Bolpur, Tamluk, Suri, Jalpaiguri, Raniganj, Ranaghat, Bishnupur, Bankura, Gangtok (Sikkim), Purulia, Habra, Balurghat, Raiganj, Coochbehar, Alipurduar, Namchi, Mangan, Gazying, Malda, Siliguri, Faraka-NTPC, Mayapur, Jaigaon, Khejuriaghat, Kalimpong, MIT Bishnupur, Singtam, Naybazar, SMIT-Majitar, Bagdogra, Chakda and Kharagpur.
Airtel 3G Coverage (speed upto 21Mbps) [Airtel has no 3G spectrum in Kolkata]
Durgapur, Asansol, Bagdogra, Bardhaman, Behrampur, Binnaguri, Chittaranjan, Coochbehar, Dendua, Dishergarh, Farakka, Jalpaiguri, Jaygaon, Kulti, Kharagpur, Malda, Lalbagh, Ranigunj, Siliguri, Purulia
[no addition since April 12, 2012]
check updated list here: Airtel 3G footprints
Reliance 3G Coverage (speed upto 28Mbps)
Asansol, Bankura, Brarakar, Behrampore, Burdwan, Durgapur, English Bazar, Haldiya, Jangipur, Kharagpur, Krishnagar, Nabadwip, Ranaghat, Raniganj, Siliguri
Aircel 3G Coverage (speed upto 21Mbps)
Asansol, Durgapur, Siliguri, Darjeeling and Jalpaiguri.
Aircel 3G speed test at Barrackpore
Vodafone 3G Coverage (speed upto 21Mbps)
Asansol, Bolpur, Burdwan, Durgapur, Haldia, Krishnanagar, Siliguri, Habra (new)
check the coverage HERE
Idea 3G Coverage via Vodafone/Airtel
Adra, Alipurduar, Andal, Arambagh, Asansol, Badkula, Bagdogra, Balurghat, Bangaon, Bankura, Barddhaman, Basirhat, Behrampur, Binnaguri tea garden, Bishnupur, Bolpur, Chandrakonaroad, Chitranjan, Contai, Dalkhola, Darjeeling, Diamond harbour, Durgapur, Farakka, Gangarampur, Gangtok, Habra, Haldia, Hanskhali, Islampur, Jamtara south, Jaigaon, Jalpaiguri, Jamuria, Jangipur, Jhargram, Jikirnagar, Kalikachouk, Kalimpong, Katwa, Kharagpur, Kochbihar, Kolaghat, Krishnanagar, Kulti, Lalbag, Macheda, Malda, Mayapur, Medinipur, Memari, Mozat bazar, Nabadwip, Niamatpur, Panagarh, Pandua, Puruliya, Raghunathpur, Raiganj, Rajbandh, Rampurhat, Ranaghat, Ranigunj, Salugara, Santhaldi, Shantipur, Siliguri, Suri, Tamluk, Tarakeshwar.
check here: Idea 3G Coverage
Partially Updated on March 6, 2013
Check out Telecomtalk's 3G Coverage Page - http://telecomtalk.info/3g-coverage-details/