Details of the proposals, which would involve EE, O2, Three and Vodafone, were made public by the UK government and industry late last week. A formal agreement on the plans has still to be reached, but the government described the prospective arrangements as "a world-first".
Under the plans, the MNOs would set up a new organisation through which they would enable each other's access to their existing telecoms infrastructure in areas of the UK where there is only partial mobile network coverage currently. The companies would invest a combined £530 million in this first element of the project, which the government has estimated would provide additional mobile coverage for 280,000 premises and 16,000 kilometres of roads.
The proposal also includes plans for the government to fund the establishment of entirely new telecoms infrastructure in rural areas in which there is no mobile coverage at all currently. The £500m investment is contingent on industry agreeing to meet government targets in relation to the first element of the project on partial 'not spots'.
The four MNOs would also be given access to existing government-owned mobile infrastructure built as part of the emergency services network to enable the companies to extend their mobile coverage into even more remote areas of the country, the government said.
UK digital secretary Nicky Morgan said: "We are determined to make sure no part of the country is left behind when it comes to mobile connectivity. We are closing in on a deal with the mobile network operators so those living in rural areas will be able to get the fast and reliable mobile coverage they need and deserve."
"Brokering an agreement for mast sharing between networks alongside new investment in mobile infrastructure will mean people get good 4G signal no matter where they are or which provider they’re with. But it is not yet a done deal and I want to see industry move quickly so we can reach a final agreement early next year."
Hamish MacLeod, director at Mobile UK, said: "The mobile industry has a shared commitment with the government to invest in and accelerate rural coverage improvements, and I am delighted that with the shared rural network, we have a proposal of action to deliver. Working in partnership with the government, all four mobile operators, through a programme of shared infrastructure, will virtually eliminate partial not-spots and then go further to bring 4G coverage to the most rural parts of the UK. This is good news for consumers and businesses across the whole of the UK."