They are only fragmented at first glance. Upon a closer look, there are organizations like the Association of Bay Area Governments, and of course all kinds of unofficial meetings and shared information sources that keep people on the same page.

Similar to how "salary surveys" are "not collusion" among the big employers, even though they're used to effectively fix the price of employee salaries to certain ranges and treat that as some sort of natural barrier like a mountain range that can't be overcome.