The fact it's taking place in "New York" really makes me think they transposed the original idea for the Plasma vs. Rocket Two-Parter into this movie, with Castelia being replaced by a different interpretation of New York, and, of course, rewriting the plot to focus on the respective Legendaries as opposed to the teams themselves.
EDIT: Also, the Official Site has a bio for Sableye on his own.
Seems it ISN'T part of the gang prior to the film, but meets Ash and Co. in the film.
And one for the gang's group (Charizard, Dragonite, the Starters, Emolga, Pansage, and Axew), and then...uh...one with some random assortment of Pokemon including Feraligatr and Persian, which I assume is probably the Pokemon Hills Pokemon.