Sadly I don't know the answer to your question. I am very curious to see if anyone does have a concrete answer.
I googled around a bit trying to learn but couldn't find any real solid information.
My intuition is that they are not treated as no follow but are actually not considered links at all. Just a guess based on their name, no experience with them whatsoever. Or something a black hat does to hide links? That would be even more obvious though... Interesting!