If you ever used Pokesav to look at or make a Pokemon you'd notice that there is a flag on them to tell you what ability they would get. In gen 4 there was only 2 options, but apparently in gen 5 there will be 3 now.
So an Adaption Eevee would be flagged with #3 and he would evolve into an Espeon flagged with a #3 which would correspond with Magic Mirror.
So an Adaption Eevee would be flagged with #3 and he would evolve into an Espeon flagged with a #3 which would correspond with Magic Mirror.