I think you've got it the wrong way round, they waited for the bus stops to be placed and then bought the adjacent properties.
You're right Jonno, there's a bus stop just outside Marks' in Muswell Hill. well, not just outside it, as they can't stop on a Zebra Crossing. And the rest of the Broadway's too congested, so the bus stop's actually about 1/4 of a mile further up near the roundabout, but the principle remains the same.