It would be a cost to those companies to lease the lines. Whether those companies are profitable or not is up to their business models. Those companies didn't/wont invest in the infrastructure to start with, which is why this initiative exists in the first place.

You think you have some sort of gotcha argument against this but you keep missing it (largely from being uninformed on the subject). Private companies aren't investing to build the infra to remote areas due to recovery cost timelines. The Govt is providing funding to build the infra alongside private partnerships to fund the maintenance and operation of the system.

There is very little downside here, if anything it avoids monopolistic control due to infrastructure investments required to service areas by providing the infra companies can then leverage in their business model.

Very similar to roads, powerlines and other things we take for granted daily that are fundamental to the operation and success of private companies.