Super Categories

Is there an easy way to create a Super Category, which can be used to categorize posts in many different blogs?

For example, can I create a category California, such that there is only one Category of that name, but many different blogs contain posts in that single Category.

Else is there a way to search for all blogs in a given Category name for a single in a site (potentially using the Multi-site Manager).

The use case we wish to meet is as follows:

1) Company A will have 1000s of blogs and many of those blogs will share category names (like a category of California).
2) Company B will also have 1000s of blogs and many of those blogs will share category names (like a category of California). Company A and Company B may have categories with the same name.
3) Company A would like a UI where a user could search for all California posts and only see the posts from Company A. They do NOT want to see posts from Company B.

Any help or direction is appreciated