I suspect the site has been rebanded.Make sure you had the correct frequencies in your scanner.
Just program it as Mot 800 MHz Standard (Type II)
855.5625 - control channel on September 12,2015
KNET316 - ULS License - Business/Industrial/Land Trans, 809-824/854-869 MHz, Trunked License - KNET316 - SOUTHERN CALIFORNIA EDISON COMPANY
Another note on this page about the system.
San Onofre Nuclear Generating Station (SONGS - SCE) - Motorola Trunked System Updates - ScanDiego.com
I'd expect it to still be in use for security, but very light use generally.Does anybody know if the SONGS system is still up and running? I know they are in the process of dismantling operations. Tried it on the scanner a few months ago and didn't hear anything. Any info is appreciated. Thanks.