BC is not hard to install. The problem is that you did not cleanly installed it. OBC and BC overlap, and OBC is much more dated. You have to do a clean install (of a mod) when updating between variations of the same mod.

Is there an open city type mod that still has author support, perchance?

http://www.gamesas.com/index.php?showtopic=1077381

Arthmoor is also working on a http://www.gamesas.com/?showtopic=1066137 that changes the layout of all the cities.

Make sure you do a clean save of BC or whatever city overhaul you are using before installing OC.

TY