Now that I think about it, I don't think carriers are allowed to block tethering apps, or any apps they don't like, anymore. (So long as they are harmless and legal)
I've had my non-root Tether app blocked on Google Play on Sprint and Verizon. When I reached out to the play store team, they indicated it was the carrier's doing.
Here are the main rules Wheeler proposed:
No blocking: Broadband providers can’t block access to “legal content, applications, services, or non-harmful devices.”
No throttling: Broadband providers can’t slow down or diminish the quality of “lawful Internet traffic” via “content, applications, services, or non-harmful devices.”
No paid prioritization: Broadband providers can’t give preference to some Internet traffic over other traffic – “in other words, no ‘fast lanes’” the FCC says. The rule also forbids ISPs from showing favoritism toward their affiliates.