Say, if you put a Haunter from Y into PokeBank and took it out into X, would the Haunter evolve?
No it wouldn´t as you don´t actually trade only save them in the internet and then take them out or not.
Source I actually tried that with Kadabra
No they sadly do not. One way to evolve them is put them on gts and ask for the same Pokemon.
Source:Experience
