Walk ons are allowed. How good of a runner are you? If you are around a 4:25 miler they will likely give you a shot.
I would contact the assistant coach. Kerr does not work at all.
The team has a good camaraderie, but don't join thinking you're joining a real D1 team. Its more like a D2 team in terms of buy in from the athletes.
But this does trickle down from the coach. He doesn't work that much if at all and leaves ALL recruiting to assistant coaches. He seemingly makes up the training plan day by day with no plan. I personally don't like his training philosophy (low-ish mileage (60s), always fast, no recovery). He also offers no individual training plans, everyone just works out together with no differences in times between a senior and freshman and a lot of times, milers will be working out with 5k guys. There is no investment from the school, its a pretty much self funded program: no scholarships, team limits still exist.
If you went to BC to run, you made a mistake. But if chose BC for other reasons, its an amazing school and amazing experience and joining the track team will be great choice. Just know its more likely you're joining a club team than a power 5 program.