Many are listed in the RR database along with the frequencies. Also, many scanners will display them on the frequencies when scanning. What NAC are you looking for, if you ask people can help you better.
Welcome to the RR forums. What specific agency(ies) are you asking about? Check the database for your area to see what's documented. NAC (if listed) would be in the "Tone" column for conventional channels or within the site details page of any given trunked radio system's RRDB page. Specific info helps us help you!