The three will now use each other's networks through inter and intra-circle roaming arrangements where they do not have licences.
"Vodafone has entered into a bilateral roaming agreement, both inter and intra circle, with Idea and Airtel to provide 3G services to our customers in the circles where we have not built our own 3G network, in order to bring a pan-India experience of 3G services to our customers," Vodafone said.
However, nobody divulged the revenue sharing arrangement among the operators.
Roaming agreements -- both inter and intra circle are the norm in the Indian telecom industry since they help a service provider offer seamless service to its customers, the spokesperson added.
"Bharti Airtel has already started sharing networks for 3G services with each other. For example they are not having 3G network in Gujarat and have started using Idea's network to provide service in that area," an top official familiar with the matter said.
Airtel, Aircel and Reliance Communications each own 3G spectrum licence in 13 of the 22 telecom circles, while Vodafone has it in 10 circles and Idea and the Tatas in nine circles.
Idea has entered into an intra-circle roaming arrangement with Vodafone for introducing 3G services in Delhi and Kolkata circles while Bharti Airtel will partner Idea in providing 3G services in Karnataka -- primarily in Bangalore and Mysore.
Meanwhile, Vodafone has started 3G services in Andhra Pradesh and Kerala through an agreement with Idea.
Uttar Pradesh (West) is another circle where Vodafone plans to introduce similar services through Bharti Airtel's network.
Similarly, Bharti Airtel has entered into intra-circle roaming agreements to share Idea's 3G network in Gujarat.
Bharti Airtel has bagged 3G licence for Delhi and Mumbai metros besides States like Andhra Pradesh, Karnataka, Tamil Nadu, Uttar Pradesh (West), Rajasthan, West Bengal, Himachal Pradesh, Bihar, North East, Jammu and Kashmir and Assam.
Idea Cellular holds 3G spectrum for 10 telecom circles -- Maharashtra & Goa, Gujarat, Andhra Pradesh, Madhya Pradesh and Chhattisgarh, Himachal Pradesh, UP (East) UP (West), Punjab, Haryana and Kerala.
Vodafone Essar had acquired 3G spectrum in 10 circles, including Delhi, Mumbai, Chennai, Kolkata, Maharashtra, Gujarat, Tamil Nadu, Haryana, Uttar Pradesh (E) and West Bengal.