Update 4 December thank you to his Grace der Graf von Luxemburg for additionally pointing out pending case C-16/18 dealing with workers employed on international trains which also travel through the host Member State.
Thank you MPI’s Veerle Van Den Eeckhout for pointing out a highly relevant reference to the CJEU by the Dutch Supreme Court /Hoge Raad. The link between the posted workers Directive and conflict of laws is clear, as I have also explained here. The most interesting part of the reference for conflicts lawyers, are the questions relating to ‘cabotage’, particularly where a driver carries out work in a country where (s)he is not habitually employed (international trade lawyers will recognise the issue from i.a. NAFTA).
One to keep an eye on.
(Handbook of) EU Private International Law, 2nd ed 2016, Chapter 3, Heading 3.2.5.