[Edi]

No, the terrain masks for maps are not the same as the site locmasks.

0 = plains
1 = small province
2 = large province
4 = sea
8 = fresh water
16 = mountain
32 = swamp
64 = waste
128 = forest
256 = farm
512 = nostart
1024 = manysites

That's what I managed to gather on a short notice offhand. I don't have Gandalf's terrainmath text file. That had all the references. You can do a test map where you put all the remaining terrains one to a province and then check the map file. Border mountain was some insane number, deep sea and cave must be 2048 and 4096 and then it starts going into the <magictype>site terrains with border mountain at the very end.