There is a very to-the-point diagram called the Hydrogen Ladder [0] that classifies the usefulness of hydrogen by domain. The author makes a good case that, despite its versatility, hydrogen is almost always worse than some other clean technology for any use case. It’s hard to make, store, and use in a scalable/cheap way, and even generous estimates of future progress show a cost curve that requires subsidies basically forever.
Buses are classified as a “Most Uncompetitive” category. Electricity, whether wired or battery powered, is cheaper and easier to scale for the predicable everyday energy use of a city bus.