The move will let GSM and CDMA operators set up common infrastructure and jointly approach security agencies for clearance in security-sensitive zones, at first only in Delhi and Mumbai but later in metros elsewhere too.

Communications and IT Minister Dayanidhi Maran, who announced the decision on Monday, also made it clear that no telecom company will be able to set up a tower in Delhi (to start with) that it can refuse to share.

Private telecom companies Airtel, Hutch and Idea and the telecom PSUs BSNL and MTNL, represented by their top executives, were present during the Minister’s announcement, made after a closed-door discussion. All said they welcomed the decision.

The move open up a fresh target market for mobile phone companies in lucrative metropolitan telephony market, which had largely-been denied because multiple cellphone towers were either a security hazard or an extremely ugly sight.

Till date, the Ministry of Communications and IT had encouraged infrastructure-sharing in rural areas, and that too outside municipal limits. With Monday’s decision, it has demonstrated a readiness to de-restrict government buildings with some basic safeguards in place.

Urban infrastructure sharing is to be mandated by the Department of Telecom (DoT), which is confident that the number of highly visible and ugly iron-and-steel phone towers will down in Delhi, for instance, from 7,000 to about 5,000 once the plan gets underway.

Mobile service companies sharing their infrastructure will also have to disguise the towers in future — as, say, palm trees — to improve the skyline. In addition, sharing infrastructure will improve the quality of services, particularly in ‘dark spots’ where connectivity in the metros is not available at all.

‘‘Dark spots and zones with call drops and congestion are to be tackled first with the common infrastructure. We are also concerned about the skyline in metros, and the operators must camoflauge towers suitably with professional help,’’ the Minister said. ‘‘There will be some controls to address security concerns, and some areas may never be opened up for operators...government buildings can be allowed on a joint basis after security clearance,’’ he said.

Delhi and Mumbai are to be a showcase for how the rest of the country will organise its metro area infrastructure sharing. To launch the process, a working group headed by a Joint Secretary in the DoT is to be set up within a week or two and results, it is promised, will be apparent in four or five weeks.

This group will also ensure that telecom towers set up in future in the metros will have technology combiners that permit CDMA and GSM operators to set up the same towers to provide connections.