Human Cell Atlas - Data availability
There is now a post on Biostars:


  We are starting to define the release process for the Human Cell
  Atlas.
  
  The first couple of HCA releases will be primarily single-cell RNA-Seq
  and we are interested to know what you would expect our releases to
  contain
  
  Please fill out our survey if you would like to help us define our
  releases
  
  https://www.surveymonkey.com/r/S6Y753P


And I suppose that answers the original question: the data has not been released yet and probably won't be for a while considering they are still discussing how to make it available.

Update (from the same post):


  The first production release of the DCP is happening in June.
  
  The first data release of HCA is targetting Q4 2018.