Yes the satnav location is from gps, the other inputs can come in from mobile masts or other information sources, such as road sensors, user submitted reports, traffic flow based on mobiles, historical data and commercial reporting companies. It will probably vary depending on the particular sat nav system being used.
Risking being told I’m Fred Drift our dogs tracker uses location from gps, and transmits that location to the mobile network, but it’s not provider specific. That info goes to the tracker company and they then transmit her location to my mobile, which is network specific. That’s one reason my wife and I are on different networks.