Interview is a sensible exploration of your understanding of their operation; no 'give us an example of when you have.......' type questions. They want to make sure that you understand the type of operation involved, the challenges you may face flying to their destinations (ATC, approach types, weather, de-icing, temperature, etc). They want you to have some idea of how the franchise system works and the benefits to both companies. But above all, they want to make sure that you will fit into the lifestyle on offer. There is the odd tech question, but nothing too grilling, afterall, you are likely to be an experienced commercial pilot if you are sat before them.
They will also ask about your life, your interests and you ambitions. I think the biggest thing for BMED is that prospective pilots must be aware of what they are getting into with respect to lifestyle and destinations, and demonstrate an interest in pursuing said lifestyle.
Good Luck
JB