If there is any policy, I believe priority is given to the highest fare paid. Then within the same fare, Plat would have priority over Gold etc.

This is what happened to me the last couple of times I was opuped out of EWR on transatlantic flights. On both occasions I was on H fare ticket.

I also remember on one of these opups another guy trying to sweet talk to the GA, showing him his Plat card and trying to get on the opup list but it did not work for him that night...

In other occasions, when I was on a dirt cheap fare, my Plat status did not help and I could see other passengers being paged to the podium and get new BPs.