I have two answers, the best one and the immediate one. The best course is to reach out to the authors and see if they will publish the LaTeX that it was used to produce that PDF (or, of course, see if LaTeX is epub aware or such).
The immediate answer to your question is that I only just now tried pdf2htmlEX (https://coolwanglu.github.io/pdf2htmlEX/) and was stunned how good it was. If you are on OSX, one can "brew install pdf2htmlex" your way to happiness. Don't get me wrong: exporting to HTML is a long way from "ebook-friendly" but I feel it is close to the spirit of your question.
Please report back if they authors do agree, as I'm sure you're not the only one interested.
