Unsure. But private LTE is already a thing where you can install your own towers onprem and configure your devices to connect to those towers instead of the ones of your standard AT&T provider (or whatever). I don't think there's any magic voodoo involved. I assume there's a way to configure 5G capable devices to connect to some local physical network you set up at a factory.

I don't expect this is for telephony, but rather a faster (I guess it's faster...) wifi. But who knows. Maybe if you install your own telephony servers or whatever you could call people on that network. Unsure anyone would care about that unrealistic usecase.