Nevertheless, it’s still true that the systems aren’t the same....
Mobiles use AGPS (Assisted GPS) involving mobile network masts to access the satellite data. GPS is always more accurate. AGPS is usually faster but still relies on having an internet connection.
Still way off the mark. GPS uses receive only data from the satellites. Basically each satellite sends out its ID and the time.
The receiver then uses a database of satellite location schedules to work out where it must be using the distance from at least three satellites.
The database of satellite locations is transmitted by the satellites at a very slow data rate. It takes about 20 minutes to transmit, but if you missed the beginning, it might take over half an hour to arrive.
Mobile phones and other devices with internet access may be able to download this data from the internet much more quickly.
In addition, working out where you are in three dimensions from three or four distance measurements is vastly easier if you already have a rough idea where you are (especially when you are moving), so using GSM cell positioning to get a location to the nearest 50 miles makes things far easier.
However, at the end of the day AGPS and GPS work exactly the same way, and the A bit just makes the first fix quicker and easier.