T-Mobile does: https://www.internetsociety.org/deploy360/2014/case-study-t-...

They use 464XLAT, basically NAT64/DNS64 with some extra cooperation on the OS’s part for backwards compatibility with apps that hard-code IPv4. You get only a v6 address, and your OS basically synthesizes an v4 network on your device in cooperation with their NAT64 router. But all the bytes going from your device through to their towers are ipv6. Talking to a v4-only website uses carrier-grade NAT64 when leaving the t-mobile network.