Priority screening DOES in fact exist at SFO Int'l A (sort of).
I fly BA a few times a year from SFO. A couple weeks ago, the agent handed me a pre-printed paper for premium passengers that entitled me to priority screening (don't remember exactly what was printed on the paper-- I should have kept it). I was instructed to go to the front of the line and hand it to the TSA agent. I did, and the agent clearly had seen this paper before, and I was straight through to the front of the line.
Now, I've noticed that as VX has added flights and more people are flying VX, the lines at Int'l A can be long (not more than 20 minutes though). This was not the case a year or two ago (at least for the European, mid-afternoon, early evening departures), and it would have been almost pointless to have a premium line.
I wonder if BA and other international airlines operating from SFO made a deal with the airport to get their premium pax to the front with these passes since there is no Fast Track security at the international terminal, and the lines have become worse?
I flew VX out of SFO last week, and was surprised by how long the lines are now at 8am. It wasn't horrible -- the security check-point at A is well-designed -- and I was through in about 15 minutes.