I've personally never had a problem getting a Carniolan accepted by an Italian colony. When I say that, I mean a standard introduction using a plugged queen cage. The only queen introduction I've ever had a problem with was introducing a queen into a laying worker hive. I went through two Carniolan queens before the third one was accepted and that was even adding green brood to the colony. I strongly believe that it had nothing to do with the race of the introduced queen but rather, that I was working with a laying worker situation.