the first 80% of the work can be a mechanical comparison:
Is the file released by AOO the same as the file that was originally part of OO.O that LO forked from.
if so, "rebase" is complete
if not, further investigation needed (and noteing the size of the diff is a good indication of how much work would be needed for that file)
I agree this could be a huge problem that does nobody any good, but the reality is that the current "dual licensed" status of LO sounds like it really doesn't mean anything from the way this article is making it sound. If there are people who do care about this, let them at least take a look and see how big the problem is to make the codebase dual-license clean.
otherwise, they may as well drop the second license.