I can say that in San Antonio where I live and also operate a ADSB receiver the dedicated air force flight trainers (T38 Talons and T6 Texans) routinely fly with ADSB on. The C5 cargo plans also fly with ADSB on when doing training but I've seen non-training flights fly overhead with ADSB off.

I can actually receive high flighting planes over Del Rio so it would be interesting to see if they are reporting bad NIC values.