Thank you Primal_Savage for not being a savage at all, but instead, very helpful and informative. My error was, indeed, not having updated to 2.0 which (when I did) corrected everything.
Actually the lairs look populated (with the icon and all) then when I get there there are no monsters. And when I end the turn, the lair icon is automatically replaced by the "treasure/loot" icon. I am 99% sure it is not at 0 or random or the ## but it will not hurt to check again :)
I am apparently doing something wrong since there are no monsters in any of the maps I play with this mod :( Any ideas? (do bear in mind that it is the first mod I try to install - unsuccessfully as it turns out)