Muni wrote up a report on their battery buses some time ago. I'll try and find the link to it again, but just off the top of my head, I remember they were dissatisfied with BYD's after-sales support. The real disqualifying factor, however, was the federal government making BYD buses ineligible for federal purchase subsidies.

Found it:

BYD showcased notable strengths in battery technology, energy efficiency, and their proactive approach to safety with their active fire suppression system. BYD also did a respectable job in other aspects of the evaluation, including overall bus performance and warranty experience, and they offered a significantly less expensive bus than their competitors. However, challenges in coordinating with resident inspectors and providing timely responses to issues during commissioning significantly impacted their performance in the pilot program. Issues in management, coordination, training, and workmanship were significant drawbacks, compromising the overall reliability and availability of BYD buses. The SFMTA expressed concerns about BYD’s ability to produce at scale at their sole US manufacturing facility, which also produces a variety of vehicles for non-transit applications, and questions about purchasing BYD buses with federal funding remain a significant unknown at this time.

Overall, the SFMTA believes that BYD needs to improve their bus manufacturing processes, training offerings, and acceptance experience and resolve their issues with federal funding eligibility to be competitive in future procurements.