Here is a general question

Is there a way to transfer your Pokemon in Pokemon Omega Ruby to Pokemon Y?

Some pokemons are compatible to transfer. However, transferring pokemon with held items that are originate from ORAS, pokemon that’s exclusive to ORAS(Cosplay Pikachu, Hoopa Unbound), and other ORAS-only content cannot be transferred/battle to X and Y. But the game will stop you before doing that tho.