as with anything in SEO, there is no actual proof that anything works or not, it is all causation theories or case studies backed up by data. Google as well as other search engines does not give spec sheets on which type of links "work" and which do not. In fact, Google recommends not building links at all!
What do you think a link from this site would get you:
It's one of the last PR10 sites left
It has always been my opinion that a mix of edu and gov links will help diversify any link portfolio, thereby normalizing it to what a natural link portfolio shoud be.
There are thousands of xxx.xxx.edu links out there that aren't worth a damn, its all about the amount of authority the page on the domain and the domain itself has, and passes onto your site.