D'oh, totally didn't realize they came with it stock. It is pretty funny when you get Fear inducing Cultists.
There is a little weirdness as far as Allies go. All the book says is they can be Brothers with the CSM book, nothing about Daemons, or Black Legion, or any other Alliances. That said, every other supplement has gotten the parent Codex allowances. Considering they are heavy on Possessed and there is bunch of fluff about Abaddon making them part of his Black Crusade, I think Daemons or Black Legion would be fine, it just needs clarification.