>>19537313There was also that Mega Gyarados and Mega Abomasnow at the start of the Mega Special that didn't appear to have trainers, although that only lasted like 20 seconds anyway so it might've just been for the spectacle.
I'm guessing that Pokemon in the wild can Mega Evolve with just the Mega Stone if they really need to, but they can do it at will if they have a trainer they trust plus the key stone. There's really not a lot of information about it yet, though.
