Looking at Mediabase, I see that WCBS-FM played Come Monday once and Margaritaville twice on Saturday, all in the afternoon.
They were identified as "new" songs for the station, which means neither are in regular rotation.
Broadening the view, quite a few classic hits stations played those two songs for the first time in a while yesterday.
Switching to the country format, I see that almost every reporting country station played Jimmy's duets with Alan Jackson "It's 5:00 Somewhere," or the duet with Zac Brown "Knee Deep." Most played both.
These were the 3 songs we played on KSKO immediately after "The Car Doctor with Ron Ananian" ended. I slept in and was a little late in hearing the news, so I slipped them in the soonest I could, and then that special aired At 9pm Saturday, airs again today.
(The Car doctor ends about 40 minutes before the usual 2 hour window is over because we strip the commercials out of it, that time on the playlist is correct)