Given all the variables used within covering certain songs and capturing as many nuances as possible or practical, you would have to (my opinion) either (a) play the parts yourself and capture the audio or midi (midi-synth guitar, keyboard, etc.) to get an approximation of the riffs, etc., then use a fairly substantial notation program (e.g., Finale, Sibelius at the high end, or Notion 3 or Guitar Pro 6 at the less expensive end) to refine notes, phrasing, rhythm, etc., or (b) play the parts yourself on each particular instrument and capture the audio. But then in the case of (b), you would have to move to Real Band, since you would run out of audio tracks in BBW.

Lastly, as I'm sure you're aware, you would also have to simulate the instruments, amps, cabinets, etc. (my opinion, amplitude and the like do fairly well, but don't come close to my guitars, Fender Twins or Princeton). And so on.

Probably why I'm content to capture the essence of a song, but still make it mine.

Richard