This morning on the front page of The Times of India I saw an advertisement for iphone 3G by Vodafone. So it will be vodafone that will be bringing iphone 3G to India and not reliance or airtel etc.
In the ad they ask you to book your iphone, no price for the iphone or the service plan is mentioned. Also this warning is printed below the ad.
Currently compatible only with 2G networks. Some of the features may not work in India.
Once you book for an iphone you will get a confirmations saying they will keep you updated about the features and prices etc.