You might have to add the buildings to the descr_items.db too - I don't think the BI buildings are in the 1.5 one. Check the tutorial section for my post on how to do that for BI (and I think you need to do it that way for 1.5 too).
Another thing: You might have to supply the physical info files, too. Not sure how it's coded in BI. But I don't think anymore you need to edit descr_walls.txt as I took another look at it and it doesn't include any faction-related stuff.