McCallister's show is marketed toward people under 25, so it's out of the demo for talk stations. There is a two hour all talk version of the show that runs live 10-12mid Sundays, along with a three hour version with several songs an hour inserted. In addition, he has a five day a week overnight version of the show with pre-recorded calls, which is much more music intensive, but the weekday show has few affiliates.
Kiss 108 runs the three hour show with music on Sunday nights. Interestingly, sister station Z-100 in New York, which also ran that version, recently dropped the program. Other stations that used to run the all talk version have pushed it back to midnight-2am. Seems that Clear Channel/Premiere will be launching a five hour Sunday night national show similar to Open House Party. If that happens, look for more CC stations to push McCallister back to overnights or drop him altogether. I could see Kiss 108 following suit.