I interviewed w/ a current student on campus, I think they mostly use students for interviewing.
You probably know this already, but BC really prides themselves on being a VERY tight community (as opposed to most other schools that tout the virtues of a large, alienated student body). So when they ask "Why BC?" you should say something like, "Well I really like the idea of a tight-knit community where everyone knows each other. I sat in on a class and was really impressed with the established rapport that everyone had with the professor and with each other, I think this would be an ideal learning environment for me."
I think each class only has like 100 people, so a big part of the interview is a check for "fit," they want to see if you're the type of person who will go out to Thirsty Thursdays and who will really be involved and extroverted.
Another thing BC loves to talk about is their alumni network -- and not just b-school alums, undergrad alums too will help you out. So be sure to bring this up when explaining why you want to go there, "Aside from the great experiences that BC has to offer while I'm in school, I know after I graduate that I'll have an incredibly strong and loyal alumni base to keep in touch with...."
My interview was pretty casual, "Tell me about what you do now and what you want to do after school," and some other easy questions. I think if you can get across the message that you will really be involved and contribute a lot, you'll do just fine.
Good luck!