The turnaround time for BU tends to vary, depending on the volume of applications they have at that time. When I mailed my application in at the end of July, they called me two days after they'd received the application to tell me I'd been admitted. My best guess is that now through June will be the busiest time for BU since this is when current med school applicants are getting an idea of whether they will/won't be going to med school in the fall (and if they won't, will be sending their apps in to SMP's). So turnaround times are likely longer.
The MCAT's definitely are not required. As Phil A mentioned above - the GRE is sufficient. You could call and ask if they''ll make an exception for you. Asking can never hurt. Worst case, they stick by their standardized test requirement, and you're in the same place you are now.
My class was size 150 (I was in the class after Fusion's). This year's is even larger, but based on conversations I've had with some people running the program, they're thinking of downsizing it again. Whether this will actually happen is a different story.