SHAKEN/STIR is rolling out very, very, very slowly. Interoperability is poorly defined and carriers seem to be sharing on an ad-hoc basis.
Anyone with a prepaid credit card can spoof numbers, make calls for < $0.005/minute, just by running apt-get install asterisk with a minimal configuration.
I'll counter Jeffrey Martens' anecdotal evidence with my own. I've had Comcast in my last 3 residences, leasing equipment provided by Comcast. In each case, performance was as advertised.
Anyone with a prepaid credit card can spoof numbers, make calls for < $0.005/minute, just by running apt-get install asterisk with a minimal configuration.