A couple of people in one forum mentioned that Avianca has given them complimentary upgrades on international medium/long haul flights (5-6 hours), even though they are not even Avianca elites, but rather *A elites (these were not op-ups, but complimentary upgrades, one person even said he got it by just asking for it).

I am a little surprised to hear that this is even possible, and wonder if there are any other airlines that you are aware that they are doing this (and how this works).