Chicago is one of my favourite Meg & Dia songs (RIP 2012). I've tabbed out a few of their songs and figured out their keys and such, but this one seems to be more than your standard vi-IV-I-V stuff. It goes like this:
Cmaj7 Bm Bb Am
Dm7 Gm7 Cmaj7
Cmaj7 Bm Am7 Eb D
Eb Dm Cm Fm Bb7
I'm 99% sure these are the chords I hear (link to the song). I'm confused between the C and C minor scales, some of the chords are from these keys but others just don't seem to fit, or at least I can't make them to.