Marion County has a dial-in system that we (indystar.com) can literally dial into (with a modem)... its a very old system and is far from 100%. We do get at least 90% of the calls mapped within 60 seconds of it being processed.
Here is how its done in a basic summary: We dial into the system with a modem, we log the data in a text file, which is then processed by a php script and sent into a database. When users visit indy911calls.com they retrieve the 30 most recent emergency calls in the database. We process the address and figure out the longitude and latitude and map it with a Yahoo mapping API. (hope that wasnt too technical).
Unfortunately, because its an old system that we dial into, the connection can become unstable and the data gets a bit 'jarbled'... after a while the scripts will recognize this and automatically kill the connection and re-establish it (which usually fixes the problems). But that does mean we have some downtime where the data is missing...