Washington Co started this way back in 2010 as they had multiple units on different channels with numerious numbers.
An example is Woodbury PD is 6xx units with reserves and part time medics in the 16xx. While fire units are 22xx and maybe on the FD or PD channel depending on function within the dept.
"I went to the doctor and all he did was suck my blood. Do not go to Dr. Acula!" - M. Headberg