I have an SMS GPS tracker, a bit different to yours but mine seems to get the GPS location from car parks.
Haven't got mine yet. Still waiting from China.
But my GPS nav loses connection whenever I enter a carpark (underground or above ground inside building). Roof-less (non-concrete) carparks I'd imagine wouldn't be a problem.
Yes, but if you mean a GPS Sat Nav such as a Garmin it uses their own GPS signals.
These GPS trackers from China use Mobile Network GPS signals and send you coordinates to type into Bing Maps, Google Earth or similar software, and work pretty much anywhere providing you can get a Mobile Network signal.