Yeah, i am guessing, everything about SEO is just guessing but it is all based on common sense. If you think about it rationally, there is no way the search engines would completely ignore no-follow backlinks, they must have to consider it in one way or another.
And what i am saying is not completely baseless, if you utilize SEO tool such as Open Site Explorer or any other backlink tool to check the backlinks of a website, for example:
You will see that they display the percentage of no-follow and do-follow backlinks. And there are also many articles from well-known SEO figures suggested that there should be a fair amount of no-follow backlinks in your total amount of backlinks.
Then again, i do not have the time or resource to conduct all these tests and researches by myself, so i can only believe what i think is reasonable