Do you mean to ask if Privs bought from ShopBB but running on T-Mobile get T-Mobile software updates? I don't believe so. I believe they'd get the unlocked Priv updates not specific to carriers.
Clearly you misunderstood my answer! I have a shop BB device and it has gotten the updates issued so far without delay! WiFi calling works ok for me most times although occasionally I have an issue, not sure if a firmware update can or will fix this. But we can hope. I have no issues sending MMS. I'm on T-Mobile.