At least around GR, the "road runner" is someone (not sure if a gov't entity or a private contractor) that does things like pick up large items on the roadway (tires, trash, fallen trees, etc). I don't think I've ever heard anyone communicate with road runner directly, but I've certainly heard it referenced by dispatchers before.
I have not heard Dispatch communicate with Road Runner, just other MSP units. In my neck of the woods, the Road Commision is responsible for clearing items out of the roadway. I have only heard Road Runner comms a couple times. If I were to guess I think it may be some type of operation?