I can't speak for AF, but DL seems to prioritize elites for op-ups on TATL flights, IME. The wife and I have received op-ups on maybe 20% of our DL/post-merger NW TATL flights since becoming PM. I doubt that is a coincidence. The rate might very well have been higher except that we have upgraded a fair chunk of flights using PMUs, as well. As another point of reference, on one recent PMU'd flight that was oversold in Y, the person sitting next to me that had been given the op-up was a GM.