Actually at this point its unclear whether Espeon can get wish with Magic Mirror due to it being an event-only DW pokemon and therefore only male, and it cannot get egg moves because of this.
Actually, Female Event DW pokemon are perfectly legal on wifi, which has a hack checker. Event DW pokemon with egg moves are also legal on wifi, which means it also gets through the hack checker. The hack checker apparently disallows any illegal combinations, although I'm not sure if it disallows pokemon of a certain gender. However, that wouldn't matter, because the fact that a DW Event pokemon with egg moves is allowed on Wifi means that it's not an illegal combination, at least this is a good assumption to make. There might be people who've found females but just never said anything, it's entirely possible. I got this info from
this post.
From this, we can still assume that Wish is legal on Magic Mirror Espeon. It can get egg moves just like any other DW pokemon.