This has been incorporated into a project to re-implement the user lists of Wikipedia:Wikipedians into a set of Categories. Feel free to help! Virtually all lists found listed as subsections of Wikipedia:Wikipedians should be eventually converted into Categories and their included links converted to the new system by tagging them in the appropriate new categories.

Userbox for New York City ((User New York City)) looks like this, and it automatically adds the user to this category:

This user lives in, or hails from, New York City.