There was a tread about it on the dfwscan yahoo group about a month ago.
It is supposed to be 700 MHz P25 and coming soon but exactly when is unknown.
The FCC database is too slow today so right now I can't check if there are any new applications filed recently.
Here is a news article about it from last summer:
County purchases upgrade for dispatch » Johnson County » Cleburne Times-Review, Cleburne, TX
These are the pre-assigned general use frequencies for Johnson County from the CAPRAD database.
The will probably be using these but that isn't verified.
769.08125
769.34375
769.59375
770.11875
770.36875
770.61875
770.86875
771.18125
771.43125
771.68125
772.08125
772.33125
772.58125
772.83125
773.63125
773.99375
774.24375
You guys in Johnson County should be searching the 769-776 range every day loooking for control channels to appear. That is the only way to know for certain when it comes online.