In my experience, generally speaking, confirmed passengers get priority above unconfirmed passengers when being reacommodated on another flight, irrespective of the class of travel, or fare basis, of any unconfirmed passengers. (A "confirmed" passenger being someone holding a ticket marked as confirmed for that specific date and flight) I have been in this situation holding a business class ticket but not being confirmed on a particular flight. In that situation, confirmed economy passengers on that same flight had precidence over me, even for business class seats where none were available in their cabin. This was the case irrespective of status with the airline.

However, I dare say it is probable that the entire manifest of passengers on this BA flight in question were confirmed and holding seats at the time of cancellation, in which case a further pecking-order emerges. Confirmed, ticketed first class passengers irrespective of fare paid will get precedence over confirmed economy passengers, which in my view is entirely reasonable (unless there happens to be a grievance passenger). Award tickets are treated as paid fares in their respective cabin of service. Within the group of first class passengers they would, if necessary, sort them according to status with BA and oneworld carriers.

To speak for BA's consistancy in these situations, the situation described in the initial post on this thread actually did happen to me on a longhaul BA flight (YYZ-LHR). We were all in the lounge, and they called all passengers holding First boarding passes, and they were accommodated on the next flight. They then called passengers holding Club World boarding passes, and so on.

When holding a confirmed First Class ticket on a flight, whether paid or award; I would as a matter of course expect that the carrier in question would regard this as more valuable than an economy class ticket. It is only reasonable that this would follow through when dealing wuth flight cancellations.