These frequencies are legacy channels from the old VHF Hi and lowband systems and are used for out of county unit interop.  All legacy channels are patched to talkgroups on the trunked system.  VCall/VTac, UCall/UTac, and 8Call/8Tac interop channels are also in use and are patched to corresponding talkgroups on the trunked system. VLAW31 (old PD National) is also patched into the trunked system.  Nationwide interop channels are found here: http://www.radioreference.com/apps/db/?aid=7742