You could listen to the input frequency, but you'd only hear nearby units that the radio you are using can pick up without the aid of a repeater. It is also worth noting that when deputies "call-in" major incidents, dispatch enables "the patch" which disables the beeping and allows all traffic to pass through the repeater on the dispatch channel; thus allowing the deputy making the crime broadcast to be heard. This is also true for major incidents requiring unit-to-unit communication. Also check out your local L-Tac channel(s), which is where unit-to-unit and unit-to-desk communication often happens. Personally, when I am scanning, I monitor the Dispatch, L-Tac, and A-Tac channels relevant to my area.
Hope this helps. Happy scanning ^-^