As Property Managers, we make sure the tile gets installed correctly. When it's time to replace, where it goes, nobody knows...right? A few years ago I had a conversation with a colleague who was involved in the early stages of carpet recycling, it sounded like a good idea, but at what cost of effort, energy, and yes, dollars, to make that happen?
As this article outlines though, the effort to recycle or re-use flooring materials is starting to go mainstream. There was even a "third party" re-use company mentioned that I googled, and it seems to be legit - a representative from http://www.repurposedmaterialsinc.com was quoted in the article. Apparently this company takes in materials and either re-use them as they are, or for a different use. An example cited was a basketball court - once it's sanded three times, it can no longer be used for a basketball court, but it could easily be used in a restaurant or other retail store.
As I have mentioned before, our company buys carpet and vinyl flooring in bulk from the manufacturer (used to be Patcraft, now is Mohawk). Maybe recycling the old carpet is not such a big leap after all.