I beleive that Restaurant cars were not allowed in international trains. At the Greek borders any JZ or BDZ restaurant cars will uncouple and a Greek one will couple up for the remeinder of the train.
It seems that the international restaurant cars were not passing the border,though there were some exceptions viewtopic.php?f=15&t=14&start=10 the 9210/9211, from 1993 renumbered to 1410/1411, was initially comming with a MAV WRm which was later replaced by the JZ one.
in the european country with no frontiers i`ll think it`s a anchronism, that restaurant cars of the BDZ are not allowed in Passenger Trains of the JZ. I`ll hope,you agree with me.