This category is populated by {{Attached KML}} (via Module:Attached KML) when the KML file is found through Wikidata. Either the article's item on Wikidata has an appropriate KML file (P3096) statement, or the |wikidata= parameter is specified (with an item id (Q-number) that has an instance of (P31)Wikimedia KML file (Q26267864) statement).