Hempy the example given,, was in response to Spodmans idea of removing the whole section on if QNH below this, this level not available etc.
Problem with adjacent FIR's isn't just when aircraft are at the boundary at the same time. Cos in our case over in the sand pit, the aircraft we are dealing with in this area are invariably YAK's, Tupolev's and Illuyshins, so the pilots have enough trouble being on the correct frequency let alone on the correct QNH/QNE.
And just for I fly who said only an issue when below 1,000 Hpa, but hardly ever below that here. We have been 992 to 999 Hpa over here for about 4 months straight now. You soon give up on saying "niner niner niner", I can tell you. At least here there is none of that silly "trip" business so triple 9 is accepted, unless talking to an aussie pilot and then they get all worried!