Leon,
I believe the pension and NEM are entirely separate; the NEM was never necessarily intended to consider a change in pension terms.
Someone in the crewroom recently seemed sure that the NEM won't provide any shockers and will provide grandfather's rights for most things. The pension doesn't because it's forced upon us by an act of parliament rather than a change in terms of employment decided by our paymasters. His impression was that while parliament can force us to accept a new pension, the NEM won't be able to retrospectively adjust your TOS.
So if you're in to 55 when it enters, you'll still be in to 55... it's the gap to 60/SPA and what happens with the poor guys who're about to hit 38/16 points and consider longer service if a promotion is now only tied to (say) service to 44.
I couldn't see ANYONE accepting promotion or PAS if they didn't include guaranteed service to 55 or beyond. Being out at 38 is one thing, PVRing at 34 is another, but being out on your ear at 44 without the pension benefits is fairly shocking.