NIKE - Remaining on the tower frequency until instructed to change to departures is a fairly general world wide practice - only in NZ is the change "automatic" (I acknowledge there will be other exceptions) - "Heavy" operators are by definition longhaul/international operators - you will notice that ATC does not in fact assume that intl departures will automatically change freq when airborne, but in fact issue a change instruction. As an NZ pilot who flies domestically within NZ (private IFR and VFR) and longhaul intl, I can tell you intl crews are more careful about R/T than a domestic pilot, in any country, who is used to only one idiom and set ofprocedures and accents etc, and are more procedural and deliberate about R/T .