Good article to read about FirstNet..
"Exactly how much of FirstNet’s licensed spectrum is intended to be incorporated into the NPSBN by AT&T under its contract with FirstNet is a carefully guarded secret."
https://www.natlawreview.com/articl...rk-nationwide-public-safety-broadband-network
If you were a carrier, wouldn't you want to harden up the rest of your network on someone else's dime? That could be sold with a 'we'll give you priority access to the other spectrum, too.'
The other story to follow is Verizon's SecondNet.