I believe we already saw something like this happen with the PG&E power outage in San Francisco in December. The waymo post-mortem [1] describes the outage causing a backlog of RA requests, which seems to have resulted in cars blocking roads an intersections. I would imagine they've improved the system after that incident, however.
[1] https://waymo.com/blog/2025/12/autonomously-navigating-the-r...