At the Air China lounge in PEK, the gatekeepers of the lounge were very focused on the BP having *G on it. I am *S. After a bit of pushing, I was able to get inside based on my full United Club membership (which had the "STAR ALLIANCE LOUNGE" printed on it).

I think if you show some *G ID card from the airline that you have *G status on, I think you should have a good chance to get it, but as others have pointed out, you technically might not be entitled to if your are not using the FFN that you have *G with.