When famous calls are allowed to stay the same after a local market split, it is usually part of the deal. That was the case between Disney and Citadel which allowed heritage radio calls to remain under the new owners. In this case, it is likely that Citadel insisted on keeping the calls as they were an important asset.
Where money is often involved is with desired calls in use on a different service. WMIA-FM is nice for Miami, but WMIA in Arecibo, PR had the calls for an AM only. The station in Miami, owned then by Clear Channel, reached a deal to share the calls and filed with the FCC.