The apps main page in the market states that conditions can be based on GPS locale. I would have to agree because I live right across the street from my university and have a gps set for on campus and my apartment and the two never conflict. When I cross the street from my apartment the phone switches profiles no problem and both locations use the same cell tower. I do not think this would be possible if it was based completely on cellular.
Yeah it does say location GPS and I'm not sure why because in the app itself in the guidelines and when setting the location, there are only 2 ways to do it and both are cellular. In addition the devs state on the website that the app doesn't and never has used GPS for determining location.