Sorry, there seems to be some confusion. PMB's, as Matty1194 points out go all the way to the top - including Internationals. What I was referring to was the obligation/requirement for the Match Observer to listen in to the PMB, especially in relation to the front rows.
As a slight aside the nature of a PMB at the higher levels of the game go beyond simply a talk just before the game. A PMB at the higher levels does have different levels of input and, for example,could involve a discussion on interpreting the laws with the coaches present and not the players perhaps a couple of days before. At NL2 and above it is not unusual for a club coach to contact the ref and ask him questions about his expectations/requirements.