If you want a quick fix; no the data from the BiaB file is not saved in the mp3 file so it can't 'go back to the sgu file' with a single click.

However, you can use the Audio Chord Wizard (in BiaB or RealBand) to determine the tempo and chords of the mp3 file .. and if you can remember the style you could easily set the A/B markers on the chords (after the ACW gets them for you) and have a pretty quick start to rebuilding it.

/only suggestion I have off the top of my head


I do not work here, but the benefits are still awesome
Make your sound your own!