I'd think of it less as an 'upgrade' voucher and more of a 'book CW for the Avios of WT+' voucher (or WT+ for the Avios of WT I guess).
I used one earlier this year for an open-jaw LHR > YUL and PHX > LHR booking in CW. Had to phone up to use it, but it was a quick and easy call and the phone booking fee was waived due to the inability to make this booking online (I hear YMMV on this).
Originally Posted by
Cap'n Benj
Is it not the case you need to book an expensive WT+ ticket in the first place, ie a T fare won't do?
I maybe incorrect but I believe that was one of the (many) reasons I binned the card off after the mega bonus period ended.
This is incorrect - you can just 'upgrade' a flight booked with reward miles (but no availability in the original class is needed).