yellowvestman,
That is all very erudite and considered. I won't comment on my individual objections...
My (simple) point is this:
Prior to 2006, the contract meant (to all and sundry), "X".
In 2006, the suggestion is that due to "Y", the contract can no longer mean "X".
My contention is that as "Y" does not apply, the contract still means "X".
Now we can argue about whether the contract was legally water-tight/ambivalent even prior to 2006, but what I don't think anyone can say, is that anybody was unclear about the intention of that clause prior to 2006. If they were, who exactly is "they"?
In this case, whatever happens if both parties seek to operate according to that common understanding, is a price they ought to pay for not having clarified the position one way or the other.
Of course, the chances of hell freezing over are probably higher....