If you are dealing with an EDACS trunking system I would strongly suggest using the AFS format (Agency, Fleet, Sub-Fleet). An example of this would be 05-123 in which the agency is the 05, the fleet is 12, and the sub-fleet is 3. A reason for using this is simply if you are searching for IDs' on a given system and various numbers come up it is a lot easier at a quick glance to see of the IDs' are associated with one another. On Nevada's NSRS TRS the agency of 05 tells me that it is a law enforcement agency but on many other systems it might be one specific entity and no other.
On many Uniden scanners when searching for IDs' on and EDACS trunking system you can specify an agency ID such as 05- and restrict the searching to only IDs' that have this 05- identifier. Thus you will not hear agencies that you do not want to hear that would have a prefix or other agency identifier such as 06-, 08-, 11-. Having less to monitor on a busy trunking system means you are more likely to hear what you want. Also, many web sites have a tendency to express IDs' for EDACS systems in this manner and not in other formats but some will show you two formats for a given ID.
Motorola IDs' are not not as complicated and presently do not provide you with the Agency search feature that I mentioned above. With most Uniden scanners and Radio Shack ones for that matter if you are searching for IDs' on a Motorola system whatever comes up is what you are dealing with and there is no way of restricting the IDs' short of locking out those that you do not want to come up again during search mode.
Keep in mind that scanning IDs' via a scan list that you have programmed into the radio is totally a different matter as you can usually label the ID to describe the talk group ID anyway you want.
Hope this helps you.