That's... not as insurmountable as it seems.
First, Teslas
don't, to my knowledge, send any ID to the charger. They just have a flag telling the charger whether they're authorized to charge, and the
car then communicates the billing info for that charge session back to the mothership. (This is actually really insecure...)
Second, CCS
does support the vehicle sending a unique ID to the charger, the VIN, and some charging networks actually use this to provide plug-and-charge, and I
think all CCS vehicles support this. (A different, and potentially worse, potential security vulnerability exists here, as VIN spoofing may be possible.)
Third, CCS also has a (probably actually secure, but also incredibly over-engineered)
mechanism using asymmetric cryptography and TLS (that is, the same tech used for HTTPS). Not all CCS vehicles support this, though.
Of course, both CCS authentication methods mean that a Tesla Supercharger install would need a data connection to the mothership that it isn't required to have to bill non-Teslas (because of the
car's connection to the mothership being used instead).