From what I've gathered, Batfamily would be a good guess. The Damian game was retooled and it could have easily been made into a MP Arkham game using the assets from their cancelled Suicide Squad game. It could also be a World's Finest game, but I think the Batfamily rumor is a safer bet, as WB loves to shove Batman down our throats.
As for the new project, I don't know which one Osama had started on, but he could've moved from the multiplayer one to a solo DC project, who knows.
The initial linkedin profile that stated their first project was co-op stopped in June 2017, so it could have been retooled as well.
Something that I DID notice that I should point out, is that
WB Montreal had listed that it needed a programmer for a next gen multiplayer new IP on its development team. I don't know whether that was for an in house project or if "development team" means that it was something outsorced. WB Montreal is a place where pretty much all the other WB studios outsource some of their stuff. A next-gen multiplayer new IP sounds like something any of the other studios could be working on, especially Rocksteady. It would be cool if someone smarter than me like
Nirolak could chime in.
Other than that, Osama did let it slip that WB Montreal has a couple projects in development, he just didn't say which was which. Holding out hope for Superman.