Changing the control channel(s) is not really an option; unless they used a control channel already in use at another site it would require reprogramming every radio in the state. Control channels are carefully selected to provide maximum performance at the location while minimizing interference to/from other sites, so changing to a completely new frequency is not a casual undertaking.
While it's possible that it's been taken down for major maintenance, that doesn't usually take more than a day unless it got totally destroyed.
If the control channels at the site are both identified (and it looks like they are), my bet is that the site has been decommissioned. Since there are no major state facilities (like a prison) near it, and since roaming users can sponge off the generosity of Miami County taxpayers, there's no real reason for them to keep it.
