I received an upgrade from ANA on NRT-SFO as a general member, not even in their mileage program, but as a general United Mileage Plus member. I'm not sure exactly why it happened, but my sister who was also general at the time confirmed a Premium Economy seat at check-in (leaving me in Economy), and when at the gate, they called me up to upgrade me to Business. It could have been because I was on a higher fare class, but I have no clue why they chose me out of all other people on the flight.