If you want the wine from J, just politely ask them (discreetly if you are in a packed section of the cabin). I think the FA goes off and checks with the ISM usually saying things like "the items for business class are strictly controlled so I have to check..." and they look up your status.

If you get a No outright, then you need to discreetly make them aware of the fact you have status in MPO. Just say something along the lines of "I've been told my club status allows this". That's usually enough to get them to run off and check. I always mention this in a long-winded fashion without being arrogant. Everytime I've got my wine from J!!!

The most important thing to remember when requesting J items from the Y cabin is to ASK, not tell. That may sound obvious but...