There was a notice put out a number of years back that the public safety agencies should stop using codes and go to clear messages. The codes were causing confusion with neighboring agencies because the code for one agency would mean something totally different to it's neighbor.
About the only way your going to find out what they mean is to make friends with someone on the agency that you have questions about. This may be a major challenge, as in many cases, they have been told not to give out that information. Maybe when you get a new police chief or sheriff you possibly will see a change.
Old habits die hard with these top dogs that have been there a good portion of their work life. You get told "This is the way it has always been done, there is no reason to change now" type of feedback from them. These are also the department managers that just refuse to use radio interoperability channels at any major event.