Publishing with APS open access with a CC-BY license on a preprint server This is a follow-up on these two questions: 
When can I safely use CC-BY license on arXiv? and
What arXiv CC licenses are compatible with American Physical Society publishing?

From the answers to these questions, it seems that it is not possible to publis an article that is already on a preprint server (in particular arXiv.org) with a CC license in the American Physical Society (APS). 

However, in Physical Review Letters (PRL), it is possible to publish open access (by paying a higher fee), and in that case APS use the CC-BY license. This license is also available for posting on arXiv.org. 

My question therefore is: If an article has been posted on a preprint server using the CC-BY license, will APS accept it for publication in PRL, either using their normal "Transfer of Copyright" (I guess not), or open-access? It looks to me as if it should work for open access, because the license under which APS would publish the article is exactly the same under which the article was posted on the arxiv.
I got a reply from APS on this issue. My question was: 


  We accidentally chose the CC-BY 4.0 license https://creativecommons.org/licenses/by/4.0/ for our arXiv preprint of a manuscript submitted for publication in Physical Review Letters instead of the standard arXiv license.
  
  Does this license conflict with the standard Transfer of Copyright
  agreement? If so, is it possible to instead choose the option "Retain
  copyright and complete the Creative Commons publication agreement"?
  
  As far as I understand, the second option should work, since APS would
  publish under the same CC-BY 4.0 license as we used for the arXiv
  submission. Is this correct?


APS answered:


  Choosing a CC-BY-4.0 license for your arXiv submission does
  not conflict with choosing the standard Transfer of Copyright
  Agreement for submission to an APS Journal.


So in short, you can use a CC-BY-4.0 license for your arXiv preprint and still publish the manuscript in PRL under the usual conditions (i.e., not open-access).