This is true of ALL very wide area trunking systems, such as multi county regional, statewide, multi state, or national systems. Some groups have statewide capability, but you will only hear them when they affiliate with a site (tower) that you are monitoring. Then there are roaming groups for regional only radios so they can still be useful in another area than thier own, again, you hear when they affiliate near you. And yet again, there are some radios that are assigned only an regional area, and do not have roaming groups, these you will only hear in that region. ISP, INDOT, SCP, IDOC, INDNR, IDEM, ISDH, FSSA, and others have statewide capability, and thus you can hear almost any of thier groups anywhere if a unit affiliates near you.