There are, of course, chords in CBS's songs, but they are sung and not played. If you want to sing one of the songs as a solo, I can see that a guitar accompaniment might be a way of keeping the harmonies they use.

One way to work them out would be the same way they put them together - by ear. If you listen to a recording using headphones, this can make it easier to untangle the parts and hear what's going on. If you can do that (or find someone to do it for you or with you) and identify the chords, there's nothing to stop you writing the chords down, either in tablature or in staff notation, for your own purposes.

Marje