I'm still hearing the site 1 control channel loud and clear on 936.225 MHz, but I'll keep an ear out for voice traffic.
Edit: Just heard 900 MHz TG 144 (this is usually patched to 900 MHz TG 240, which is Distribution South 1 "DS-S1" dispatched by "Station A"). This is being patched to RCS SDG&E TG 119. A single patch radio ID exists on the RCS talkgroup for all the voices, which indicates that the radio traffic is originally occurring on the 900 MHz SDG&E system and then being patched over to the RCS.
Long story short, the SDG&E 900 MHz system is still alive and well. You may have just caught them at a slow time.