Twenty years ago, there were no CB radios in the CHP Communications Centers. CB radios were installed in the Commercial Enforcement Trucks for communication with the Truckers to direct/instruct them where to pull over or for other related enforcement communication at the Officer's discretion.
At that time, I would guess that there were no more than a handful of Patrol Units statewide that had a CB radio installed. Also, at that time, there were plenty of room inside the vehicle to install a CB radio because all the radios, emergency lights/siren, radar, and MDC were consolidated into a system consisting of a Screen, Keyboard, and the Microphone. The day when the Patrol vehicle had multiple radio control heads were gone by then. The Computer CPU/Controller was in the Trunk.
Some Inspection Facilities and Platform Scales had CB radios, but none of them monitored Ch. 9. They were usually monitoring Ch. 15, 17 or 19, the Trucker's Channel, depending on their specific location. I don't believe anyone monitored the Trucker's channel 21 in Souther California.