You might consider that a lot of people won't download any of these mods at all. Additionally, it would make a lot of sense to just incorporate the christmas mod completely into SRB2TP.And considering that SRB2TP will be using that music as well as SRB2 Christmas and the Christmas mode mod, you're going to be downloading the same music files 3 times and wasting more space than had the music not been removed.
EDIT: OK, actually it would not because SRB2TP doesn't feature SRB2's current levels. You could still offer the music file as a seperate download that every of your mods uses as a resource.