Initial Article:
Report the article refers to (15 pages including the sources):
http://www.eecs.qmul.ac.uk/~hamed/papers/PETS2015VPN.pdf
Thought it was a semi-interesting read (the article). I'm still sifting through the report. Section 6.3 (Page 12) addresses use with Tor.
It's unfortunate that you can't really guarantee you are safe from big brother watching over you. VPN's are great and they do help with your privacy but if you really did have something to hide then you would have to go all out to keep it that way.