Since it came, up, quick lesson on the Blues plans.
Each BCBS is a separate license. The Blue Cross Blue Shield Association, based in Chicago, administers the licenses, assists with coordination between the different companies, etc. BCBSA is not an insurance company.
There are, I believe, 37 companies currently which hold the licenses and are insurance companies. Obviously, one company may hold multiple licenses. Anthem holds a lot, I think 15+. Health Care Service Corp holds 5. Others are only one, IE BCBS Michigan is one company, one license. These different companies are separately managed, do not cross into other territories, and have various legal structures. That is one reason why you'll find so much variation from state to state - it frequently is different companies.
If you're curious, BCBSA's website has more information.