Buses on Quantum Schedules
maa.org
maa.org
What isn't mentioned in the article is that not only isn't there a schedule, but often times, there aren't even labeled bus stops -- there is just a route. So, it encourages another sort of optimization: people looking for a ride tend to clump. If you're on the corner by yourself and you're not able bodied or don't aggressively jump on the bus, you may be waiting for a very long time. Also, these micro-bus will pass each other by going "express" and skipping whole blocks of potential riders to resolve a clumping issue.
The routes themselves are fixed by some sort of agency, and there is a union that, with seniority each driver/company gets assigned to lucrative routes. The article claims the micro-bus are owned by the driver. I don't think this is that common, typically drivers are hired and paid on commission. Although it is true that Pesero are independently owned & operated.
In Poland most of the buses have many doors and passengers board and leave vehicles quickly. In Oxford, boarding through front doors means that the first bus may stay on the bus stop for several minutes.