The trunked systems in that area are listed at the bottom of the page
All Trunked Radio Systems in El Dorado County
System Name Type City
AT&T (Formerly Pacific Bell and SBC) LTR Standard Various
Crystal Communications LTR Standard Rescue, CA
Cumulous Communications LTR Passport Various
Day Wireless Systems Motorola Type II Smartnet Folsom
LaRue Communications (Rescue) Motorola Type II Smartnet None
Nevada Shared Radio System EDACS Networked Standard Various
Pacific Gas & Electric Co. LTR Standard Various
Signature Wireless LTR Standard Placerville
SMR Tadlock & Associates LTR Standard Sacramento
The more interesting stuff above that since it just has the frequencies isn't trunked.
The names like Motorola Smartnet II are the trunking system used so you if you want to listen to that system then you have to find a scanner that supports it.
My area for example
http://www.radioreference.com/apps/db/?ctid=2060 lists fire and EMS frequencies but has this at the top "The Delaware County P25 800 MHz system is now on line and in service. The VHF fire/EMS frequencies will continue to be used for dispatch paging and mutual aid crosspatch only, but most of the below frequencies will be removed from service" So I can still hear a little bit on the frequencies listed but I need to upgrade to something that will do P25. You can go to their wiki and see what each type is, for example the P25 is a digital trunked system.