Yesterday I changed the origin of a Xurkitree (not an evolved Pokémon) from Japanese to Italian and it was flagged as legal, but the A/O was written in Japanese (I noticed it in game).
EDIT: Well, the situation was a little different from what you have written: I changed the origin of Xurkitree in Italian, and his name was "Xurkitree" as expected, but the A/O was in Japanese, and it's impossible. It's not possible even for evolved Pokémon (the country origin must match with the way the A/O is written)
Edit2: I'm sorry for my bad English, I think it's not A/O in English xD
I meant, the original trainer (O/T maybe?)