I can't believe I forgot to mention WKDD and WAKS. While they serve two different areas, in reality their towers are less than 10 miles away from one another. 'KDD covers 70 DBU over Cleveland and 'AKS covers Cleveland and Akron equally well. They could simulcast one another if they wanted to. "96-5 and 98-1 KISS-FM, Northeast Ohio's Hit Music Leader!"
Except that WKDD is Hot AC and WAKS is CHR. While playlists are somewhat similar, they do serve two different purposes, and is not at all unusual. See iHeart in LA (KIIS/KBIG) or Philadelphia (WIOQ/WISX) for example.