Nothing protects Sony-BMG from being sued by you for redistribution on a CD except that putting the redistributed version under the same license. This means that they wouldn’t be able to prevent EMI, Warner, or Universal from also issuing a CD with your song, and the version of your song on any of these CDs would be licensed under BY-SA, just like the original.

However, the CD as a whole isn’t contaminated, so for example the cover art is not automatically BY-SA just because it’s packaged with your song.