Port-a-lucine in Dementlieu, Blaustein, Hazlan, Bluetspur, and one other, Carnival?, are already in the server already, and even with an insane number of areas and a pretty healthy playerbase the servers been working reasonably lag free.
It looks like they've got something set up for Forlorn as well, but that may just be a temporary area for an ongoing quest right now.
So, five, possibly six other domains are already supported, but at the moment only Barovia is accessable outside of DM events. Port-a-Lucine and Blaustein are supposed to be getting added as full areas in the near future, so you'll get a chance to see more of the great work our Devs have done.