I don't think it always works. We were OWE and in blue. Didn't matter as we were in J, but I wonder whether we would have been bypassed for free drinks in Y. Boarding passes all correctly reflected BA OWE. The ticket was a BA coded one on AY J, so I wonder if that made a difference.
I hear they've been having issues with codeshares. I wasn't recognized as a Platinum when flying AY on CX code.