While browsing through RR forum, I ran across this thread. Yes, I've often wondered how listeners obtain detailed fleet map information, etc. for statewide P25 or MOT trunking systems.Most of the information comes from us (scanner) users -- using the SEARCH functions of our scanners.
Search and find CONVENTIONAL frequencies -- monitoring and determining who the users are (police dispatch, fire dispatch, etc.).
Search and find TRUNKED system control channel frequencies -- then either use a program like Pro96Com (free!) and/or program the control channel frequency the look for new trunked system talkgroups.... followed by the same as above - try to determine who the user of each talkgroup is.
Most importantly of course - is to take the time to submit the finds to Radio Reference -- so everyone else can use the information.
Use that SEARCH functionality!