If BMI can post competitive fares
But they won't be able to, without losing an awful lot of money! Passengers in Europe are unlike American travellers and as such do not have the excessant love affair with small 50 seat jets.
Park the EMB145 next to a Q400 and you're right, most people will pick the jet, however show them the respective prices charged and they'll pick the Q400 everytime. Cost is key, to the airlines and also to the passengers that fly them! They will go for the lowest price!