Neither of those agencies use NXDN or DMR, they are on the Viper P25 system. As for NCDOC, yes they do use NXDN but if you are more than a mile or so away there is little chance of hearing them as it is a low powered system for use in the prison.
There are some federal agencies using DMR, like the USPS sorting facilities, but it is mostly used by businesses and some local governments. Please keep in mind, the website you listed in your first post is a great source of information, however it is taken right from the FCC files, not what is actually in use. A local college here in Raleigh was listed in that site as being DMR for about two years before they actually made the switch. That is the advantage of the RR database, submissions there are supposed to be verified by listeners, not based on just FCC records.
That said, if you can afford to add it you should, it is better to have it already installed rather than finding you need it and not having it.