The battle lines for the next big corporate war in the telecom sector have been drawn. And the warring Ambani brothers have come together to take on incumbent GSM operators on the issue of refarming 900 Mhz band spectrum. Both Reliance Industries and Reliance Communications have supported the move to refarm spectrum in this frequency band. Old GSM operators including Airtel, Vodafone and Idea Cellular have opposed it. The views of the operators have emerged from the submissions made by them to the Telecom Regulatory Authority of India.