Subsidized Transportation

Many cities have programs that give free or discounted transit passes to people in need. Unfortunately, many cities don't have frequent enough transit to rely on. 

Can subsided Ubers fill this gap? If you're only picking up 3 passengers an Uber is far more efficient than a bus. And if these roads weren't densely traveled enough to warrant frequent transit they probably have extra capacity. And better than subsidising cars directly, because of efficiency gains.