I'm in for 10. I just signed up for my Avios account and while my e-mail receipt shows my new number on each ticket, MMB does not. I assume this will resolve as noted above.
I guess there's little risk here - IB promised to deposit 9,000 miles into our accounts within 10 days for each booking. If they do not, I believe a credit card dispute would be appropriate, which should cost IB something on top of the refund of the tickets for not fulfilling the terms of our agreement.