I don’t think google is doing anything particularly nonstandard, they basically wrote the standard. RCS requires a server for the device to talk through, and google has been the main server most devices use. Some mobile carriers hosted their own but found it wasn’t worth the effort since google would do it for them, and the encryption is such that carriers didn’t have much to monetize.

Even if google was doing something nonstandard, the amount of begging they’ve put in to get Apple to support RCS means I’m sure they will do everything on their part to ensure interoperability on their end.