I've not heard of any issues receiving calls when on wifi. I know several people with Moto X's in the lower mainland, none have any issues. The RF performance is outstanding on this phone. Of course we all have XT1058s and not the XT1053 but it should make no difference as they are using the same bands for calling here.
Have you tried a different phone in the same area?
Have you made any mods to your phone at all?
Have you tried resetting it to default?
Deep in the Heart of the State of the Art with my Moto X.