[Edi]

The common Trolls & Vaettir poptype (61) that allows recruitment of normal trolls and vaettir is randomly available but it is just very rare. I actually had a province with that poptype right next to my capital in LeafNosedBat. And to add insult to injury, the Troll Pit site I found was in the same province!

I have never seen poptype 66 which only has vaettir in it, but it could be very rare like 61. I've seen 61 three times total, once win Dom-PPP, once in Dom2 and once in Dom3. Poptypes 67, 70 and 71 which have Vaettir with the Dwarven Smith or Svartalf or which have pure trolls are not randomly available but can be added to a map file with the #poptype <nbr> command. The same is true of the Asmeg poptype (69).

All other poptypes can appear randomly, though the Toad tribals are about as rare as the trolls and vaettir in my eperience.