The Kiwis tend to classify the whole route in quite broad terms compared to other rating systems (at least that's the way it strikes me) and they address both objective and subjective factors so it's not terribly easy to compare to other systems. Probably best to describe the grades, so I found this:Standard grading system for alpine routes in normal conditions:
New Zealand Grade 1: Easy scramble. Use of rope generally only for glacier travel.
New Zealand Grade 2: Steeper trickier sections may need a rope.
New Zealand Grade 3: Longer steeper sections generally. Use of technical equipment necessary. Ice climbs may require two tools.
New Zealand Grade 4: Technical climbing. Knowledge of how to place ice and rock gear quickly and efficiently a must. Involves a long day.
New Zealand Grade 5: Sustained technical climbing. May have vertical sections on ice.
New Zealand Grade 6: Multiple crux sections. Vertical ice may not have adequate protection. Good mental attitude and solid technique necessary. May require a bivvy on route and be a long way from civilization.
New Zealand Grade 7: Vertical ice/rock which may not have adequate protection. Rock grades in the high 20's (Ewbank). Climb may be in remote area. May require a bivvy on route.
(The reference to Ewbank is the Australian system which is much easier to find comparison tables for. They seem to often use Ewbank when they want to be specific about how hard the crux is, but I haven't been able to find a Ewbank Grade for the summit rocks - probably because Ewbank was never envisaged to describe mixed climbing). Hope that helps.
Scan down this page for some photos of that section:http://climbforhope.wordpress.com/previous-climbs/