Available public and semi public spaces are very directly related to homelessness and mass transit is such a space. I've lived in a variety of places and people still continue to use mass transit even if occupied by someone who is homeless. The issue is that doing something for members of society by undertaking free transit has to be coupled with tactics that address the inequalities that allow homelessness to be pervasive or to consume resources that aren't really meant to deal with homelessness.