Regional wireless carrier C Spire has told the FCC it doesn’t buy T-Mobile’s plan to bring low-cost fixed wireless service to rural consumers.

T-Mobile, which is in the midst of a merger with Sprint, announced plans to launch a $50 per month fixed wireless access (FWA) service pilot to select rural consumers, and promised to expand the service after its merger with Sprint is complete.

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C Spire and the Rural Wireless Association (RWA) responded to the announcement in an FCC filing that argued T-Mobile’s promises do not take into consideration the economics of backhaul in remote areas. They suggested that T-Mobile lacks sufficient backhaul capacity in rural areas to support T-Mobile’s current represented coverage and speeds as well as New T-Mobile’s 5G plans.

C Spire and RWA are both part of the 4Competition Coalition, which opposes the merger.

T-Mobile responded with its own ex parte filing March 11 (PDF), arguing that some portion of its rural sites already have high speed backhaul, and that the rest are awaiting contracted fiber build-out. “Additionally, T-Mobile has future-proofed its backhaul to handle the performance requirements of New T-Mobile with scalable/upgradable solutions and contractual arrangements already in place,” it said.

C Spire volleyed the ball back over the net with a second FCC filing (PDF), claiming that T-Mobile’s FWA plans ignore the realities of backhaul. “There is nothing about the proposed transaction that changes the challenging economics of doing a green field build in rural areas where the availability and cost of backhaul present severe limitations,” it states.

C Spire went on to say that, despite T-Mobile’s claims of future-proofing its network, “no copies of the contractual arrangements have been provided, and no details of the arrangements have been offered. No timetable is given as to when any backhaul upgrades will be completed and, as before, no commitment is made as to the nature and extent of New T-Mobile’s rural build-out in any particular time frame.”

Without these concrete assurances of T-Mobile’s plan, C Spire said it believes the FCC should “dismiss T-Mobile’s lofty claims that New T-Mobile will commence a robust rural buildout.”

T-Mobile and Sprint are hoping for the merger to be approved by the second quarter of 2019, which is just now coming out of a three-week shot-clock pause.