There are some files where the locations of .CAS files are specified - you might need to edit those.

bi\data\models_building\list.txt
bi\data\settlement_plans\barbarian_large_city.txt
bi\data\settlement_plans\barbarian_huge_city.txt

Do a search for ".CAS" in each file and where you see a path like...
Code:
street_plan	../../../bi/data/settlement_plans/street_plans/barbarian_large_city_pathfinding.CAS
...either cut the "bi/" bit like this...
Code:
street_plan	../../../data/settlement_plans/street_plans/barbarian_large_city_pathfinding.CAS
...or replace it with the name of the mod folder you are using. There may be more files like that that I haven't spotted.