Pokebank just came out in the US a few days ago, but when I got it two days ago, I didn't get the Event Celebi... I traded Pokemon from W2 to, but I still didn't get the Celebi... Why did this happen?
you first need to get the BP or pokemiles using the link button on the tittle screen in Pokemon X and Y then go to pokebank after getting a poketrasnfered Pokemon and you´ll get celebi
You get Celebi the second time you access PokeBank. The procedure this Stack Exchange Gamer ran were:
**Click here for the Screenshot
If you do those steps, you will probably earn that much-wanted Celebi.
Hope I helped. :) Source