A landline call is routed directly to the call center (by the telco's CO, I beleive).
So while yes, the cell phone knows exactly where you are (better than gps with a CDMA phone), and sends that to the call center, the data often just falls on the floor. Of course, if you're calling from a car, driving down the highway, your location quickly changes.
So don't call in an accident without stopping at it. It just wastes everyone's time.