I don't know. I qualified based on UA status, which I believe requires any Premier level but not non-premier base membership. I saw somewhere at some point a list of participating airlines, but now the official website for the program just says "Ask your airline." But in UA's case, I can't imagine anyone you could talk to at UA would know anything about it, perhaps with the exception of the local Hong Kong sales office.

I think as a general rule of thumb, most major international airlines that serve Hong Kong participate. I would be surprised if any airline that doesn't actually fly into Hong Kong participates, even if they have an alliance partner that does.