"There needs to be a process in place for the relevant telemetry to be easily available to crash investigators in a standard format, and I doubt if anyone has started work on that yet."
Yes, something like a montage from the onboard cameras with speed and acceleration/braking in the OSD on a 10 minute loop? That should be very cheap to add to the cost and complexity of an AV since it's ust a few extra wire and a device the size of a USB pendrive. It could probably record obstacle proximity info quite easily too. 10 minutes worth of that basic data would almost certainly cover 99% of incidents.