i don't know if I am supposed to know this, or if its even related, but the federal prison in El Reno had the same thing happen a couple years back, when they changed over to digital, and lots of people with scanners were ticked off about it.
All the Federal Prisons are going to be Digital. They are in the process of doing away with the old 170 Mhz radios at many of their facilities now.
The Bureau of Prisons is making those moves to 400 Mhz trunked as soon as the funds are
available for the equipment.
It is just a matter of time and the old analog systems will be collecting dust in some warehouse waiting to be sold at some GSA auction or given to a foreign country to use.
I've heard traffic on both 163.200, and 164.600, recently. 164.600 is normally much lower power, so unless you're in their area, you won't hear them operating on this freq.