firewall, I suspect that the overflying oceanic traffic, would have continued as planned. There are however also multiple non oceanic traffic climbing and descending which in this day and age is a very different cup of tea to control procedurally. I worked in a procedural ATCC back in the late 60s when the volume (and speed in many cases) of traffic was a great deal less than today. Then there's the question of training and maintaining currency for an event which is likely to occur only once in a blue moon. No, the best solution is that which was taken.