As you know, Google hosted an AMA with the Google Brain Team yesterday on Reddit and I went through the 742 comments in the thread to pull out any references to search, RankBrain or rankings and honestly, I found nothing.
All I discovered was that the Google Brain team doesn't want to talk about RankBrain.
Besides for the generic mentions that their team did work on search and it was called RankBrain, I found these two other remarks:
From Jeff Dean at Google who said we don't talk about RankBrain and search:
That being said, there are some kinds of research work where we don't necessarily publish details of our work (our work on machine learning for our search ranking system and our advertising systems, for example).
From Greg Corrado at Google who said he worked on RankBrain, which was a way they used machine learning in a practical way:
One of the things I really like about working at Google is that there's flexibility to work on a mix of pure research ideas and real-world applied projects. For example, I got to collaborate on a project to called DeViSE, which aimed at learning to identify a photo of an object based only on reading a wikipedia article about that object (totally nutty research)... and then collaborate on a project called RankBrain to improve the quality of Google Search results (totally practical). I feel like moving back and forth between research and products infuses us with creativity and energy.
That is really it, unless I missed something. You can scan through the comments yourself on Reddit.
I honestly felt we would hear more about this but I guess I was wrong.
Forum discussion at Reddit.