When I was a member in Vinton, the 154.085 was the primary channel on "high band". This has been switched to the 155.055 for whatever reason. The second channel, now being 154.085, should be used for rescue administration but all members have access to it. John is correct in that almost all members carry portables and it is connected with the low band paging for a short period of time after tones are set out. Members can mark enroute to the station or the scene. Usually dispatch will not acknowledge this as it is to time consuming, although dispatch does have the frequency and will monitor in case a member comes on scene before the unit, etc. It is used heavily for logistics.
The Vinton police no longer have the mobiles in the cars. They also used to have 15 or so portables on the "high band" and I don't know if they still have those. These were 154.860 and 154.875. It was used primarily as backup in the event 800mhz went out. Animal Control also was strickly on high band, but has been on 800mhz for quite some time now.
All the rescue portables and mobiles also have 155.205 (statewide rescue mutual aid) and 155.340 (H.E.A.R) along with a base station at the Rescue 2 with these.