Yes it is. Coverage based on tower locations for this include Eaton, Evans, Garden City, Greeley, Johnstown and Windsor.
853.575 is currently used for voice on the 35th Ave site. Ironically this frequency was the primary control channel frequency used for the Windsor site before it was shut down during the upgrade to 9600 for DTRS years ago.
Past observance leads me to believe they are in a testing phase.