Hmm.. my GPA and mcat score are in my mdapps. I volunteered in a pediatric office, had a leadership role in a campus organization, had a pretty unique job while in college (completely unrelated to anything medical/science-y) and mentored/tutored kids through an outreach program. I spent a long time making sure all essays in my primary and secondary applications were as well-written as they could be (including the writing quality of my activities section). I'm also very interested in medical humanities (art, literature, etc) and emphasized that in the mssm secondary.
Also, once I got a C+ in an organic chemistry class. My non-bcpm GPA was way higher than my bcpm GPA. So I guess you can get an interview even with grades like that. I'm not sure I would've been so lucky if I didn't do well on the mcat, though.
I can only speak from my own experience, but it definitely seems like Mt Sinai looked beyond my numbers.