It would probably be fairly simple to do this to most Western tonal music (at least now that someone else has done the hard part and written a tool that automat

It would probably be fairly simple to do this to most Western tonal music (at least now that someone else has done the hard part and written a tool that automates the process!), as the biggest factor I see in keeping the sound coherent is the timbre and texture of the sound, not necessarily the actual music. Most pop/rock/etc music has (at most) a single key change, which means that 75-80% of the song uses the same 8 pitches over and over again. Add to that the rather homogeneous sound of modern pop/rock/etc instruments (not to mention the limited range of vocal styles usually applied within a single song) and I'd guess this would work with most "popular" music written over the past 50 or so years. There would certainly be exceptions (Bjork, for example, probably has enough textural vocal changes within a single song to make this much more difficult), but by and large, I'm guessing the output of this experiment is more a commentary on modern pop music theory than it is the specific stylings of Nickleback.