The only other time I can think of was the 1994-95 NBC/CBS/Viacom/Westinghouse/New World/Fox Television sale-o-rama, especially in Philadelphia where NBC and CBS swapped with KYW going to CBS to eventually be purchased by them via Westinghouse, NBC bought WCAU from CBS to swap stations in Denver and Salt Lake and the Channels 4 and 6 towers in Miami, and Paramount/Viacom sold to Fox who almost bought WCAU.
Surprisingly you very rarely find ABC in these though. They barely grew after the Cap Cities acquisition, and only bought two more stations just to cushion in case ABC went to UHF in Detroit, which they since sold off.