Transit agencies don't have the technical expertise to distinguish truth from lies in cleantech marketing. They aren't the only ones, see the over-inflated valuations of both Nikola and Tesla as two (very different) stories of companies successfully lying to investors and the general public about the magical capabilities of their novel transportation platforms.
They kind of do, though. Most transit agencies hire consultants to plan out these transitions, and the consultants have expertise in the different technologies and can present the pros and cons. However, the decisions stemming from this information can often be dictated by the transit agency's governing board, which cares less about this fat report that they just paid for and cares more for the hydrogen interests whispering in their ears.
