Hi Stephen,
I have to admit, I don't understand how a branch category relates in any way to bibliographic information.
Thanks for your kind attention and answer, which clarifies to me the scope of Branch categories. For some reason, I ended up by confusing and mixing the roles and scopes of "Item types" (well described by BWS Johnson's very helpful "Koha. A newbie's guide", which I am following), and "Branch categories", which were not covered by Johnson's guide - simply because they are probably a feature of newer releases of Koha. (I had, for some reasons, speculated about the possibility of having different branches of a same library dealing each with different subjects or even item types, e.g. books or CDs.) Thanks again. Giuseppe.