Salem Fire
If you don't want to go through the computer upgrade, and want a simple way...
Just monitor them in CONVENTIONAL mode.. NOT trunking. (be sure to lock and unlock the control channel as needed each day.) There should be 4-5 800 frequencies you can manually enter into your scanner. Salem Fire is on A-tower system 99% of the time. (If A goes down then they would switch to B.)
A Tower System isn't all that busy in the day, but you will hear buses, and public works at times. At night after 5-7pm, you will hear Fire almost exclusively.