sounds like a datastream not a control channel. but i could be wrong. i haven't heard anything like that before.
I live in Marin County and public safety here uses a fairly new Motorola Type II Smartzone TRS with IMBE digital voice. On one of their new radio sites, I was hearing two control channels at once - One normal Smartzone CC, and another one that sounded very similar to that (kind of like a Type I CC but with even more time between peaks). I was told that it was some kind of datastream generated by the motorola site trunking equipment as a test signal for radios.
That could mean nothing and that datastream could actually be the control channel for some proprietary trunking system nobodies ever heard of, but I think the best way for you to tell would be to scan the other freqs for voice and then cycle through modes in your scanner to see if there's any underlying CTCSS, DCS, Motorola or even LTR subaudable data below the voice traffic. The Golden Gate Transit radio system threw me off for a while since one of their channels carries data for GPS vehicle location and tracking of their buses, but it's actually a conventional system. That one freq just sounded like a control channel which made it appear that GGT was trunked, although in your guys' case with Monterey/Salinas the license says they're trunked so they probably are.