From here. http://bulbapedia.bulbagarden.net/wiki/Talk:List_of_glitches_in_Generation_VI#Friendship_Evolution_Glitch
Apparently, some people who transferred Pokémon that can evolve via happiness from one Generation VI game to another using Pokémon Bank were never able to get them to evolve, even when they were at maximum happiness.
However, PokeMaster99999 doesn't rule out that this may have been a glitch that was patched out in a later revision of the Generation VI games.
I may have some Pokémon in Omega Ruby from X that can evolve by happiness that I've transferred already. Since on one of my Nintendo 3DSes Omega Ruby is still on version 1.0, I could see if in version 1.0 a Pokémon can't evolve by happiness, and if it can on version 1.3.
Though I know close to nothing about how Generation VI works, I do know that there is a new part of the Pokémon data structure that stores the latest OT (not the original OT) of a Pokémon. Perhaps, food for thought there is/was a bug in Pokémon Bank where that isn't updated when you transfer a Pokémon to another game and that is responsible?