Would it be so hard to manufacture your own hydrogen on-site with the $20k plug and play electrolysis setups they sell to labs and industries? You can just plug into a high wattage outlet and let it work when the grid is at low demands

You can't drill for oil & refine it at a bus depot but for the case of hydrogen maybe the assumption that fuel has to come from a supplier can be challenged

I don't see any benefits from economies of scale for electrolysis