The hydrogen fuel cell is a pipe dream economically, and they will continue to be a pipe dream for decades, or even centuries to come. It's simply unviable, there's no other way to describe the system.
Some on here may recall Perths hydrogen fuel cell bus experiment, which ran from 2004 to 2007. Three Mercedes-Benz buses fitted with Canadian Ballard fuel cells were purchased with Federal Govt backing of more than $3M.
The W.A. Govt also provided a lot of money and infrastructure to run the buses. Hydrogen was produced from the Kwinana BP refinery and trucked to the Transperth bus depot in Malaga.
This was not a widespread hydrogen distribution system, there was only one point of hydrogen dispensing, which limited the buses movements.
The program was called the STEP program (Sustainable Transport Energy for Perth) and the fuel cell buses were provided to multiple countries to see how workable the design and system was. Perth was the only Australian location to use them.
The fuel cell bus global trial was a Mercedes-Benz initiative, designed to see if they could produce the buses as a long-term viable product, globally.
The hydrogen fuel cell buses were generally regarded as acceptable, with satisfactory reliability - but overall, operational costs were high, and routes were limited due to lack of an extensive hydrogen distribution system.
The fuel cells were found to need expensive reconditioning every three years, and three year testing of hydrogen tanks was another cost burden. The trial ended with no substantial orders for the fuel cell buses.
Full scale production of the fuel cell buses was abandoned when Mercedes-Benz deemed proceeding with the fuel cell bus design was uneconomic. Transperth made the decision to simply convert diesel buses to run on CNG, and about two-thirds of Perth's bus fleet has been CNG-powered buses. The CNG buses have proven reliable, and lower-cost to operate than either diesel or fuel cell buses - although there were early teething problems with bus fires using CNG, because of an initially bad CNG conversion design.
Today, electric buses are deemed to be the future of mass transportation. Perth's Public Transport Authority has been operating Volvo electric buses for 2 years now, with great success (18 have been operational since last year), and has recently placed orders for another approximately 130 Volvo BZL electric buses.
The Kwinana refinery (once, Australia's biggest refinery) has since been closed down, so one cheap source of hydrogen locally has been removed. No-one has developed a sustainable hydrogen-production operation in Australia yet, even though we've been promised that "cheap" hydrogen production for over 20 years. No cheap hydrogen, and no distribution system for hydrogen, so where's the benefits of hydrogen engines or fuel cells?
https://www.bpswa.org/hydrogen-fuel-cell-buses.html
https://www.busnews.com.au/inside-the-mysterious-first-australian-hydrogen-bus-trial
https://www.pta.wa.gov.au/news/media-statements/first-year-of-electric-bus-travel-in-perth-a-success
https://www.transdev.com.au/press-release/new-electric-buses-for-perth-cbd-routes/
https://minister.infrastructure.gov.au/c-king/media-release/wheels-turning-manufacture-new-electric-buses-wa