It doesn't contact Garmin. It's a shared emergency response center akin to some home security system companies. They share with a few tracker services.
Update: The use GEOS https://www.google.com/search?client=firefox-b-1-d&q=garmin+...
Update: The use GEOS https://www.google.com/search?client=firefox-b-1-d&q=garmin+...
edit: Thanks!