ScanDiego.com

Here is a sound of it:
http://www.kb9ukd.com/digital/modat.wav

I'm not aware of anyone in San Diego using it.
LAPD had them before they went digital and I've heard it on some 39 MHz freqs during skip season.

Admins note: Incidentally, this guy 'Gary Hahn' has a rather nice collection of Digital Mode Samples at one level closer to the root of the URL Brandon posted. They can be found here:

http://www.kb9ukd.com/digital/