It all depends on what is programmed into the 800 radio. The remote head in the back obviously takes over the radio up in the front cab. So the medic giving a patient report will switch control via the remote head. I know that on a fire mts2000 portable some law channels are SD 1, 2, 3, 4. Park Rangers, and EGPD 1 and 2. I haven't seen any CHPD or RCPD on the radios. EGPD is under "local" or something like that, and SD is under Law. again this info came from a Sac Metro MTS2000. the typical zones are Fire A, B, C, D, and T. Local gov (which has EGPD), Law (which has SD 1,2,3,4, and PRs). And the hospitals.. that's all i remember off the top of my head. there are alot of "hidden" channels..like EGPD in the local gov zone. ill flip through all of them someday and write them all down. i know that's a lot of somewhat irreverent info but i hope it helps.
but i do get the same problem you speak of, i think it is a glitch of the scanner itself, because no one responds saying "your on the wrong channel..."