It's confusing
I have had success with the following combinations in Y (and more)
AY ticket MA Gold (!)
BA ticket, BA Silver
BA ticket, AY Gold
AY ticket, AY Gold
AY ticket, BA Silver
LH ticket, AY Gold (!!)
Basically it depends on the guy checking the b/p's
Monday I'll have an AB flight, will see how it goes. I'll start with BAEC G and if rejected trump it with AY+ G