Originally Posted by brunos

As Guy Betsy said, the two seats will return to CX yield management upon cancellation. Depending on what the software decides, they will be reopened, or not, as award.
When you book hundred days before departure, CX tends to offer the awards first to their AM members. If there are CX members who waitlisted, they will get them. Otherwise, they will be temporarily be only available for CX members. If they are not taken within a week or two (or more), they might release then to BA/AA members. Hence booking on Avios 355 days ahead and hoping to get them again two months later on AA is far from assured.