Mostly this was driven by the merging of fire districts and a four digit numbering system didn't align with the larger PRP, Fern Creek and Anchorage/Middletown. At risk of being labeled an old has- been dinosaur who doesn't like changes, "they" probably could have massaged the old system. That said, a new CAD system was put into place that may have also been a factor.
An unintended/unforeseen issue has arisen as the new CAD won't accept four digit numbers. So there's a little issue with neighboring counties when they come in on mutual aid. They are scratching their hands on that.