"Though it is too early to say that MTNL is cross-subsidising, if it is proved we might take it to the highest adjudicator, including the Supreme Court," an official with a top cellular company told The Financial Express.

Another Mumbai-based official in the cellular industry said, "We have written to the Telecom Regulatory Commission of India (Trai) asking for clarification on the issue."

However, it is not yet clear whether they have done it under the aegis of the Cellular Operators Association of India or on their own. But, if it is established that MTNL is cross-subsidising, these cellular operators might take it up with Trai. As of today, the cellular operators have to pay the basic operator (MTNL in case of Mumbai) Rs 1.40 for a three minute call made from the cellular to a landline phone.

Trai will find out whether Dolphin (MTNL's mobile service) pays a similar amount to MTNL basic service.

Industry sources don't seem to be entirely convinced that it is possible to offer mobile services at the rate announced by MTNL, namely, Rs 1.50 and Rs 2.70 for an incoming and an outgoing call respectively.

The Trai guidelines very clearly say that there can be no cross-subsidisation and regulators globally have been very sensitive to the whole issue of cross-subsidisation.