I'm no scientist and a lot of my knowledge on drugs is "experience-based", so I don't always, or usually, have straight science to back up a lot of my experiences or observations, but I'm familiar with the peculiar interactions between alcohol and Opioids. Besides the obvious, being alcohol's enhanced depressive synergy when consumed with Opioids, it seems that being dependent upon Opioids seems to definitely change the way we experience and the effects that we get from alcohol.
I like William Burroughs but I don't worship him like some people. His books provide some useful insight on a lot of junkie-related topics though. In his book "Junkie" Burroughs discusses his lack of desire to consume alcohol while being dependent upon Morphine/Heroin, but later on in the book, when he is forced to come clean, his desire to drink alcohol returns and he notes clearly that the experience of alcohol's effects are significantly more enjoyable without Opioids in the system. Later on he becomes a piss-your-pants drunk for a time.
I've experienced the same phenomenon. While I'm on Methadone Maintenance or otherwise maintaining an Opioid habit, alcohol has absolutely no appeal to me and the thought of it can even make me sick to my stomach. Whereas, when I'm not maintaining on any kind of Opioid, I can get a really euphoric experience from a few quick drinks and have fun going out drinking with friends.
I don't know how to explain the phenomenon, but it's a real thing and I've known others who have shared the same experience.