Is there a working solution to produce PDF/A-1b with MiKTeX?

Answer posted as a comment on November 10th 2016 :

Finally, with the latest version of MiKTeX (pdfTeX, Version 3.14159265-2.6-1.40.16 (MiKTeX 2.9) and pdfx (v1.5.4) it works out of the box.