On my 12th June post, i said IDEA CELLULAR is the next GSM operator coming to Kolkata. But in a reply to TelecomTalk.info one user says IND 036 is tata gsm as seen in his mobile. other source is http://www.42it.eu/Mobile_Systems/SMS/Coverage/India/ which also says 405 036 is Tata GSM, ie Tata DoCoMo.
SORRY for the WRONG INFORMATION :(
But strange thing is Tata Tele said their GSM service will roll in south states and then western and nothern India, they did not mention about launch in eastern zone, at the same time Indiatimes report ( http://timesofindia.indiatimes.com/Kolkata-/New-players-may-lower-mobile-call-rates-from-Pujas/articleshow/4537001.cms )saying idea planned to come to kolkata in puja time.
but idea network is not ready even, it's sure the testing network active over kolkata is Tata GSM !