From the IAG statement of 22/12/11
“bmi regional and bmibaby are not part of our plans and Lufthansa has the option to sell them before completion”.
Regional doesn't fit with any BA operation and Cityflyer have enough problems to worry about without having to integrate another aircraft type and 180 aircrew on different T&Cs. I would fear for Regional's future if they were forced into the IAG deal.
BA don't have any use for it and 50 seat jets into LHR is commercial suicide, so I can't see where it would fit for BA.