So reading the article it sounds like this is just a catchy headline. They're not seriously looking into building them:

“Despite significant engineering hurdles, it is conceptually feasible to operate buses safely at high speeds under controlled conditions,” the review reads. “However, real-world implementation requires incremental approaches, substantial investments in infrastructure, technology, and rigorous validation through field tests.”

“It might offer as a complementary option alongside existing solutions like rail, not to replace them,” Mehdi Moeinaddini, a senior transportation planner at Caltrans, told KCRA about the high-speed buses."