There's two things here I must note:
1) As long as they're ID'ing as "Urbana/Springfield/Dayton", their studio only needs to be 25 miles from Urbana. Otherwise, they have to move their COL. It does NOT have to be INSIDE Urbana proper.
2) The transmitter must be within, I believe, 15 miles of the COL, and the signal MUST cover their COL with a city-grade signal.
Beyond those two major requirements, everything else is moot. They can shout "Springfield and Dayton" to the heavens if they wish, as long as they're ID'ing with their primary COL FIRST and the transmitter/studios meet the distance requirements.