I would think that http://img62.imageshack.us/img62/7466/mapmorrenormous.jpg got the MoT crash effect right.
After that, Vvardenfell erupted, and everything in Red mountain, perhaps a bit further was instantly covered in lava. (Ald-Ruhn, Maar Gan, the Zainab camp, and perhaps Tel Vos is gone)
The lava goes into the parts of the land where lava had previously been (forgot the name <_<). There are certain parts where these paths quickly stop. There's one near Balmora. The lava would either burst over into Balmora, or go the other way, to Lake Amaya, where everything is already destroyed, thanks to MoT.
Gas starts to fill up the air. There's plenty of time for most to escape. There's always someone with some skill in each city to teleport others, and there has to be at least one with a sense of decency to help the others.
I estimate the places with a chance of survival (not certain) to be:
- Gnisis
- Ald Velothi
- Khuul
- Dagon Fel
- Tel Mora
- Tel Ahrun
- Tel Fyr
- Sadrith Mora
- Tel Branora
- Hla oag
- Gnaar Mok
- Balmora
- Caldera
Balmora and Caldera are kinda 50-50. There's a chance that the lava will burst out too quickly, but it may not. Due to being so close to the ashland, it's hard to tell.
Places on islands have the highest survival chance. The lava has a harder time getting through water than over land. These places are usually Telvanni, too. They have a lot of mages who can teleport people.
Also, it's quite a while later. There has to be more, bigger towns all over. And Vvardenfell is already way bigger than represented in game. There's more people around, it's more than likely there's one mage who'll teleport people out.
There has to be a good hour or so for the teleports to be done. It will take some time for the gas to reach each city, and for the lava to burts over, and get to the outskirts of Vvardenfell.
The northern tip of southern mainland Morrowind is destroyed by MoT. Mournhold Survives. People don't realise Vvardenfell has erupted yet. By the time they realise, hardly any have escaped. (unless the Vvardenfell refugees go to Mournhold for some reason)
Everyone hears news that Mournhold has been ravaged by lava. Everyone starts to teleport out. The Argonians hear. They decide to start attacking the southern cities. The guards put up a fight, but eventually get beat. The Argonians take a lot of Dunmer hostage, but die when the gas gets there. Is it just standard poisonous gas? If so, the Argonians are fine.
This is all just my opinion. I don't think enough died to make Dunmer an endangered species. Being able to see it early was a great advantage to those in Vvardenfell. The east and west mainland was fairly ok. They managed to teleport quickly.