It's easier to understand the US Congress than it is to understand priority "stuff" when it comes to the interaction traunked radios systems and scanners.
There are different types of trunked radio systems, as you have seen. If it is a Motorola system, the manager of that radio system (that's the "system manager") can set talkgroups up to be priority talkgroups. For example, fire talkgroups can be priority over dog catcher talkgroups.
If your community is using a Motorola trunked system and that radio system's manager has set up priority talkgroups in that system, you could take advantage of that with your scanner by using Preemptive Priority ID Scanning.
Let's say your community's Motorola system has set Fire Talkgroup 1 as a priority talkgroup. You have programmed your scanner so that Fire Talkgroup 1 is a priority takgroup/channel. If you are listening to Dog Catcher 1, and someone begins transmitting on Fire Talkgroup 1, then your scanner will jump to Fire Talkgroup 1.
So three conditions have to be present for Preemptive Priority ID scanning. 1-Motorola trunking system, 2-talkgroups have to be programmed in that system to be priority talkgroups and 3-your scanner is programmed for those talkgroups to be priority. If any of these are missing, then priority scanning on your scanner is a little different.