I've been trying to upgrade LAX-LHR on NZ from Premium Economy to Business Premier using *A (LH M&M) miles but found that A booking class is not upgradable. I'm wondering if it's possible to upfare to O (which is the next lowest booking class for PE) so that I can use miles for an upgrade to Business Premier. I've been told that only U,E,O,Y & B booking classes can be upgraded.

My fare must be either ALX21AP3 or ALW21AP3 and according to KVS:
THE FARE MAY BE USED AS A CREDIT TOWARDS ANY HIGHER NZ FARE WITH COLLECTION OF THE FARE DIFFERENCE.

Has anyone been successful in upgrading from Premium Economy to Business Premier with *A miles by upfaring first? I got the impression that seats were available and an upgrade could be processed rather than waitlisted but I may have been optimistic.