I fired away some questions to Macecraft (authors).
Based on their documentation ByteGuardian looks purely an ECD calculation and ECC using utility.
It's not a backup program per se. It has no idea how to extract partly unreadable files of a cd-r/dvd-r disc, but assumes that these kind of "broken" files are somehow available and fully accessible on the HD along with the intact ECD data.
It solves half the equation so to speak.
I'll report back when I hear more from them.