A large proportion of people will not willingly share their commute space with others. Since people who "vote with their feet" seem to prefer to drive their own cars in privacy to sharing a vehicle, route and schedule with other people the rider may not like, it will take more than engineering to get the intended result. It will mean, eventually, either outlawing ownership of private cars in certain places or making permissions prohibitively expensive.
I see a big, expensive failure in this. Nevertheless, it will get funded by groups who are obviously against union labor: the Koch brothers, government planners, et al. Retailers like Wal-Mart, on the other hand, will be against, as they have few stores within cities, and it's hard to lug their stuff home on a minibus. Amazon and other internet sellers will see the same cost-without-benefit scenario.
The winners? Media outlets who will see an increase in revenues of "for-and-against" political ads.