Nintendo has confirmed that to download the Pokémon Bank App and use the service gamers will require a Nintendo Network ID
Outside of Pokemon Go, Shiny Celebi will become unobtainable when Pokemon Bank closes - until that happens, here's how to get one.
Shiny Celebi was available via movie promotion event. Dexoys is the only one you gotta worry about shiny because it can on be shiny in original gen 3 carts. That being said, they arent closing bank down. This was already stated multiple times.
Shiny Deoxys is currently exclusive to Generation 3, which means it'll become unobtainable once Pokemon Bank closes.
Pokemon Bank is presumably closing soon, and several Shiny Pokemon will become completely unobtainable afterward.
...how else would it tie to your account? I fail to see how this is anything but common sense.
The only reason I'm downloading it is to get Celebi.