Every 24 hour PSAP in the state of Missouri has access to MOSWIN through radios placed in the PSAP by the state with federal funding. Those radios are installed in almost if not all locations now. With 150+ talkgroups pre-programmed into each one, the "basic load" that all MOSWIN radios are expected to have, this will provide a way to call HIPO, Adjacent county PSAP's, not so adjacent counties PSAP's, and other users on the system.
Every radio has a county talkgroup, that all users in that county will have, active on the towers that cover that county. They will also have county "travel" talkgroups, that will allow transport cars, EMS units, and others with a VALID purpose to have short checkins with their home agency. (Don't envision a local fire chief checking in on the channel that he is out at the hotel in St Louis, and the weather is nice up there)
Then the interop talkgroups, on a county, region, and statewide bases the interop and event channels are in each basic load.
Those talkgroups are outlined in the Wiki.
Every level 1 and level 2 radio will have these.
Level 1 users will also have their own talkgroups, dispatch, operations, etc.
Level 2 users will have the basic load, for mutual aid and interoperability.
So, yes, every county will be on MOSWIN, just to varying degrees such as level 1, 2, 3, 4, 5,