I seem to recall a story about cell phone companies not meeting a federal requirement that they be able to triangulate and determine the location of 911 calls from cell phones. This was at least a couple of years ago.
I would have thought that they'd have been doing that by now.
A lot of cell phones do have this capability. When my husband was in an accident his phone locked up and had the tracking system on as soon as he called 911.
Future cell phones will be required to have GPS receivers to transmit exact geographical coordinates. It will be illegal to use a cell phone that doesn't.