Y="Specialty" (hopefully a little nicer than a regular model in that class) so YB="Specialty Compact" which is kinda ridiculous but yes they have Specialty Compact and have for at least a few years. Also YC, YD, YF and I think after that they give up on the Y prefix. I hope there's not a YA as I can't imagine what that would be but there could be. I don't even know what is typically in the fleet for A anymore, have not even booked one because B or even C is always so little price difference that I don't bother.

So I guess nothing conclusive yet that the Mazda 3 will be a C since clearly at least some are still YB.