I've said it a number of times here before, but BNSF has deployed NXDN to several yards. Off the top of my head there are NXDN systems in Denver, Memphis, Argentine Yard, KC LPC, Barstow and Los Angeles. It's not fully utilized in all those locations, but the systems are in place and are active.
I have a buddy that I hired out with who works in Denver, and unless its specific to a craft, he hasn't heard anything NXDN and still carries a 2180...
Not saying that its not there, but its not in "Widespread" use as I indicated, mostly due to lack of equipment in the field that is setup for NXDN. Its localized if anything. Plenty of cab radios that are not setup, optioned or capable of NXDN in the field (though plenty of JEM's out there, just not enabled based on my experienced).
Until the waysides are cut over and actually used over the road, its still a toy. My contact over at Amtrak has stated the same thing, even in their good radio coverage area's. No one likes the high BER rates when your walking a 15,000 ft train in rolling hills or in mountain territory. Hell, you can't even do that now in analog.