A bicycle is the way to go. New Yorkers do seem to come together in crisis. Maybe have a bike messenger (there are a few in Manhattan) assist with B's escape/journey out of town. Maybe help with a flat tire and then route planning.

Note: I've never had a flat tire on my bike, so I've never had to fix a flat on the side of a bike path -- but I don't ride skinny road tires. I rode 2" slicks in DC; I highly recommend them for any commute where potholes & cobblestones are common, and where curbs may become obstacles.