I actually thought the Items where the only ones used... and the .cas's CA had left behind in the BI folder where irrelevant once the item was made?
taking an example the
BI_barb_stables_lvl_4_lod1.CAS's etc you'll find they are listed in the extracted version of descr_items.txt that Alpaca posted eg:
and the resulting
is in the BI/data/items folder (you can see from code example that its incorporated the various lod levels into one item)
I've not tried running without the BI cas's still in the folder but as RTW doesn't include its cas models I'd assumed they were redundant....