I've just booked an itinerary involving one BA sector, one AY sector and two BE sectors. I booked it all at ba.com and throughout the booking process it showed all four sectors with their BA flight numbers. As I understand it, that means I earn as if they were all BA flights, including cabin bonus, tier bonus etc.. The confirmation e-mail also shows BA flight numbers, but when I go into MMB only the BA sector shows a BA flight number, and the number of Avios points it says I'm going to earn is consistent with the operating carriers' rules, which for one sector in discount Economy means I'm set to earn 25% of base mileage instead of 200%.
Have I misunderstood the rules or is what it says in MMB wrong? I understood from the sticky that if my booking confirmation shows the flight number with a BA prefix then I earn exactly as if it were a BA flight. If the prefix makes no difference then I think I'll cancel under the 24 hour cooling off period and rebook through the Finnair site at a substantially lower cost!