OZ and KE both will also upgrade anyone if the flight is oversold/full. I've been lucky twice on KE for oversold flights GMP-KIX and ICN-MNL. The last time I flew OZ to HKG, I forgot to ask and I definitely saw others with Seat 1C marked Economy in their boarding pass.

Unlike the U.S., if you ask politely if the flight is oversold, they don't roll their eyes. They offer politely to check and will do it if possible.