Much like G4, these change their names when they evolve. They are still japanese, and gain experience as such.
However, SOME pokemon do not change their names (see Bond's pokemon for example) - this is possibly because they are nicknamed, but possibly because they are cloned with Pokesav which "loses some information" - I'm thinking it tricks the game into thinking their real names were their nicknames, which is why those don't change when they evolve.
Because of this, I'm thinking of removing all of the Bonds pokemon from my thread; but at the same time everyone else is trading them so I'm inclined to think they're legit... even if they are "read" as nicknamed.