Never went there in X/Y. Makes more sense here. Confines you to the city. Offers a different environment for you to find Pokemon in a logical habitat.
Leans towards no, despite this. Agrees on something like Poison, Dark, and Ghost types down there. Glanced at the map on the website. Shows Chandelure and Aegislash above ground, with no real thought for habitat. Sees no obvious sewer access points on the map. (Does not know what that would look like, to be fair.)
Presumably would have shown off an environment like a sewer/underground for the trailer. Remembers Krokorok in the trailer above ground. Scattered trash bins around for any Trubbish-y Pokemon. Recalls some spooky house in X/Y, which could house Ghost types.