As someone who works with multiple carriers, I doubt anyone outside of the wireless carriers and Inteliquent will implement STIR/SHAKEN soon in the USA.
Inteliquent (aka Neutral Tandem, Onvoy, Exiant, Vitelity, plus 20 other sub-brands) is the only provider implementing this protocol outside the cellular industry, and most of the CLECs they work with are not capable of maintaining SIP with a TLS certificate, let alone their own PKI as STIR/SHAKEN would entail.
Yeah, it's mostly wireless carriers at least for now. Already T-Mobile and I think ATT are rolling this out to consumers, called Certified Caller ID I think. However, the FCC is coming down hard on all carriers for this. I don't know if there's any fines for not having it implemented, but I know Chairman Pai said he expected it to be implemented this year. Obviously, telecom moves slow and it's not possible for all carriers. Even some SBCs I'm sure don't support it (specialized call handling hardware). It will be interesting what kind of legal requirements they put in place with regards to this. I think they will try to strong arm all carriers soon.
