This question arose from a question about print on demand books in libraries. I tried to find out how many libraries have books of print on demand publishers, such as Lulu, Blurb, and BoD. Unfortunately I was not able to do such search in WorldCat. So the general question is how to search for publishers in library collections to find out whether the books of a publisher can be found in many libraries or not.
The supported list is buried in the Help. See: http://www.oclc.org/support/documentation/worldcatlocal/expert_examples_WorldCat_Local.htm