You might do that with an 'Automatic Sweeper':
In the script editor, click on the flash icon in the Options column. In the upcoming dialog, select an 'Autom. Sweeper' lib, which is a cartwall library which should be used as an automatic sweeper library.
If set, a sweeper track is automatically selected from that library (matching/less than the ramp time of the related track picked by this script-line) and added as an 'EndsWithRampOfNextTrack' track insert-transition to this track.
Alternatively you can simply place directly in-front of your xmas script-line a related xmas-jingle script-line, ie.:
Cartwall, Xmas-Jingles, Count=1
Random, Xmas-Tracks, Count=1
...
Finally you would have the option to use so called Station Voice Files (which associates a fixed track to be played before or after a given music track), see here for details:
viewtopic.php?f=9&t=38