I don't recall how the Whistlers handle private call DMR (they don't properly track DMR or NXDN systems, only listen to & pass traffic on the voice channels individually) but the Unidens handle tracking DMR private calls fairly well:
Only caveat is you need to make sure the 900mhz radios aren't frequency-hopping spread spectrum radios (as is the trend now with Walmart and other retailers). If they are then you won't be able to follow traffic on a scanner unfortunately
Uniden