Each library does, but unless they already all use the same software and have someone who knows it well enough to export the data and they have the time to do it, I suspect it would take a long time to collate the data in a useful form. And that assumes the books are keyed by some kind of unique ID like an ISBN in all libraries, otherwise good luck collating the different spelling/typos of titles.
Just reaching out to all the libraries and getting them to submit the data would take a lot of time.
Don't libraries know the books they own? That seems unlikely, since they need to know that when they lend them out.