US operator C Spire argued T-Mobile US won’t be able to fulfil a promise to vastly expand rural coverage in the wake of a proposed merger with Sprint, noting the deal won’t change economic factors which make it costly to run backhaul to remote sites.

In a filing with the US Federal Communications Commission (FCC), T-Mobile stated it has “substantial high-speed backhaul capabilities for its rural facilities” and “concrete plans” to upgrade those facilities to meet the needs of its post-merger network.

It detailed plans to upgrade its existing microwave backhaul links to support multi-gigabit speeds starting this year, and noted several scalable solutions have been installed to ensure the network is “future-proofed”.

However, in its own filing, C Spire contended those declarations “do not demonstrate that new T-Mobile will actually obtain the backhaul necessary to construct new sites in rural areas”, and noted the operator did not address how it would overcome financial barriers to rural deployments.

“There is nothing about the proposed transaction that changes the challenging economics of doing a greenfield build in rural areas where the availability and cost of backhaul present severe limitations,” it wrote.

The question of whether or not the merger will help expand rural coverage in the country has become a sticking point for T-Mobile and Sprint as regulatory reviews of the transaction plod along.

Though T-Mobile has promised to deploy a more robust network in remote areas following the merger and build 600 new retail locations to better serve small towns, sceptics have questioned the specifics of its execution plan.