The GeoCrumbs extension was installed on the Wikimedia Incubator back in 2013 (T46725). However, it doesn't currently serve any useful purpose – the way the extension works, subpages take precedence over the extension's {{#isin:}}magic word, so that the breadcrumbs for "A/B/C" will be "A > B > C", regardless of whether there is an {{#isin:}}tag there or not. So in essence, all this does is to duplicate the subpage links that are already built into MediaWiki core.
I don't know if it ever fulfilled its purpose, but nowadays it doesn't.
I am making this request as a consequence of T316108; the Incubator is most affected by that bug, since all content pages on the Incubator are also subpages.