To which purpose? Whom does this effort do any good?
- First there is no easy way - at least none I'm aware of - to tell the images treated with tone curves and those that haven't.
A professional photographer may have several 10,000 images in his directories. Time is money for pros.
- Which workflow do you intend to use?
Going ahead with the imported catalog, transferring to process version 2012, take advantage of softproof, a new way (a better one, of course) to manipulate the images in Development
keep the photos you "tone-curved" in LR 3?
Why on earth do I want to do that?