Yes, you should be able to book them as soon as they go to BA flight numbers.
Just tried it and you can indeed book these on ex-bmi flights (BA8xxx) as reward flight savers. Once they have the BA code then BA consider them genuine BA flights not a bmi codeshare (there's no BD code on the flights anyway).
Last edited by layz; Jun 18, 2012 at 10:45 am