I believe that the southern boundries forthe Hayward Office (25xx units,Aqua) are I-880 @ Dixon Landing Road and I-680 @ Scott Creek Rd. and pretty close to the actual countyline bountries.
The southern boundries for the Redwood City Office (91xx,Amber) are somewhat confusing. The US-101 boundry seems to be at SR-237, where the San Jose Office(24xx,Ruby) picks up south of SR-237. The I-280 bountry seems to be at the I-280/SR-85 Interchange, where San Jose picks up I-280 south of SR-85 and the Monterey Office picks up SR-85 south of I-280. The stretch of SR-85 between I-280 and US-101 seems to be covered by San Jose, however Redwood City takes alot of the calls if San Jose is 10-6. It appears that Redwood City covers alot of northern Santa Clara county around the SR-85 corridor.
The San Mateo Bridge is a strange one, but this is what I have witnessed. The units that handle incidents on the eastbound side are handled by Redwood City, along with any eastbound radar traps where they sit at Pier 1 and anyone of the substation pullouts and radio ahead to the (citation writing) unit usually located at the Toll Booth/Hayward side. These speed enforcement units work simplex on the Amber because they can work their details and be in position for any eastbound speeding/reckless/drunk driving reports. Any incidents on the westbound side are dispatched from the Hayward side since they are most likely in position to respond. It the incident location is sketchy, then both sides will send units until the exact location is determined. Ditto that for any Fire & Rescue units that are dispatched also. There is also the lone Hayward unit that parks in the Tool Booth parking lot and shoots radar at the eastbound traffic as the cars leave the bridge, he will most likely be on his primary channel (Aqua). The RWC units that sit on the westbound (Foster City) side right after the bridge will be on the Amber.