I've had at least two experiences in this area. Once traveling IAH-EWR-MAD in Y, the Houston -Newark flight was very, very late coming in, and several of us literally ran to the MAD gate. All boarding had been completed but the GAs were waiting (there were 5-6 of us off the IAH flight). Panting and fumbling for my OP Plat card, I asked "Is there an oversold situation? Are you upgrading any Plats?" You would have thought that any battlefield upgrades would have been already given out to speed the boarding process. "Oh!" said that GA looking at my boarding pass. "Mr. Spainflyer, you've already been upgraded." And off I went to 1B.

Another time at EWR I left the PC and went down to the gate early because the MAD flight was clearly oversold, and the agent in the PC had confirmed it was. I approached the counter very quietly and asked in some innocence: "Would you be needing a seat in coach?" "I've got one!" called out the GA to the red jacket -- who was wearing grey as I recall -- and they seemed very happy to start the battlefield upgrade process with me. Don't know what would have happened if my OP card had been Silver instead of Plat.