This is bus (and light rail) transit in California. Or it was. The state is slashing transportation funding, so local transit agencies are having to cut routes and raise fares. The impact this has, unfortunately, is to cut ridership. This also makes more areas of the cities inaccessible to those who don't have cars.
Which makes the scenario posed by SB 375 rather unlikely: how to build density around functionally non-existent transit corridors, or those that are so lightly used that they are discontinued as bus routes, leaving the massive developments behind?
There needs to be not only Federal transit funding reform, but an intelligent approach to permanent transportation network development. Transit-Oriented Development (TOD) is actually a way of planning that links nodes of existing density in a way that uses proactive land use planning tools to integrate the most effective transitways. Excellent approaches of this kind are outlined on the Human Transit site. How to actually do a corridor study that results in effective land use and transit planning is covered in another post on this site. The transit must be permanent, and with a means of maintaining it built into its funding structure. If the state does not intend to fund transit, then it has no business requiring dense development for the non-existent transit, especially those developments that presume that everyone will get out of their cars. Holy smokes.
So it's really a very synergistic and feedback-loop kind of an issue, and simplistic approaches like slamming density around any bus route is a guarantee of failure in community strategic planning, not to mention a waste of money. That's not how transit planning and strategic land use planning is done; it's a far more complex process than that, with too much at stake to allow single massive projects to overtake an urban or suburban landscape. That's what created sprawl - subdivision tract-mapping that never provided the schools, service centers or public spaces that should have been the drivers for development. People need a reason to go places. Simple as that.