Like David said, they have to say "WCFS Elmwood Park" in the Top of the Hour ID. If they want to say WBBM AM and FM Chicago in their TOH ID, they'll have to change the call letters, and the City of License also, which the FCC won't do. WCFS is considered a First Local Service to Elmwood Park. Elmwood Park is a substantial City. The FCC has refused to change COLs to nearly nonexistent communities in favor of more substantial communities, mainly at the behest of competitors, for trying to move the TL to a location where it would serve a substantially larger population and city and serve it somewhat with a 70 dBu contour, but the 70 dBu F(50,50) would no longer serve the nearly nonexistent COL. One had well over a dozen other commercial 5 mV/m and 70 dBu commercial signals covering it. They might have tried to use Longley Rice prediction now that it is more widely accepted.
In other cases, the companies have owned enough stations and made deals with other broadcasters to replace the "move in" with another station, by swapping COLs between stations. That is hit and miss unless you own numerous signals in an area. Otherwise, I guess you could put another station into Elmwood Park. But it has to already be Licensed to Cover and on the air before that could happen. And an existing station would have to have more than one station in its COL.
The illusion of commercial service to lesser COLs is usually just that, an illusion. And any Rural Radio Initiative would really have to change 92-108 MHz rules to like Canada has, to allow lesser facilities without distance separation requirements, only contour requirements. NCE-FMs in 88-92 MHz have much less stringent F(50,50) service reqirements. Numerous commercial full power stations in thinly populated areas have gone off the air, and many have been deleted. I'm not sure that LPFMs are powerful enough to serve larger rural areas, and they are also noncommercial.