Fundamentally, the ICAO Annex I rule is you log everything blox to blox as P2/Co-Pilot/local equivalent.
Just to add to the confusion, Annex 1 states (my emphasis):
"2.1.9.3 The holder of a pilot licence, when acting as co-pilot at a pilot station of an aircraft certificated to be operated with
a co-pilot, shall be entitled to be credited in full with this flight time..."
I'd interpret that to mean that a co-pilot can't log the time unless he or she is at a "pilot station", so bunk time doesn't count.