Both companies jointly own about 20,000 towers with tenancy ratio of 1.65 as of June 30, 2017, the firms said in a statement.
Hit by a bruising price war and the goods and services tax (GST), Vodafone Group Plc's India unit reported a 39 per cent fall in pre-tax profit at Rs 4,075 crore for the first half of the current financial year.
"Both Vodafone India and Idea as customers, and ATC TIPL as a mobile network infrastructure provider, have agreed to treat each other as long-term preferred partners, subject to existing arrangements". "The parties will work together to further the expansion of high speed mobile networks in India", the statement added.
The statement said that after Vodafone India and Idea have completed their merger, around 6,300 co-located tenancies of the two operators on the combined standalone tower businesses will coalesce into single tenancies over a period of two years without the payment of exit penalties. It is acquiring Vodafone's towers for INR38.5 billion ($592 million) and Idea's for INR40 billion ($615 million), with the transaction due to go ahead in Q1 2018 once it receives all necessary approvals from regulators.
Idea and Vodafone's Indian unit are now merging in a move that will see them overtake Airtel as India's largest telecoms operator with more than 400 million subscribers.
American Tower, which agreed to take control of Indian masts operator Viom in 2015 for 76 billion rupees, has been steadily expanding its presence in India - the world's second biggest wireless market with 1.2 billion mobile subscribers.
The entry of Reliance Jio in the telecom sector has led to a wave of consolidation as the financials and margins of existing players have come under enormous pressure.
For the quarter ended 30-09-2017, the company has reported a Consolidated sales of Rs 7461.90 Crore, down -8.53 % from last quarter Sales of Rs 8157.40 Crore and down -19.75 % from previous year same quarter Sales of Rs 9298.88 Crore Company has reported net profit after tax of Rs -1190.90 Crore in latest quarter.
The company's ARPU (average revenue per user) stood at Rs 146.