The fire truck had lights and sirens on according to updated articles, so the Cruise vehicle would be at fault
So the cruise vehicle could have failed to handle the situation as well as a human driver, but it's also possible that the emergency vehicle wasn't driving carefully enough.
Why did you say "could have" instead of "did"? Are there circumstances in which it is acceptable (and/or legal in the USA) for a car, autonomous or manned, to drive directly into the path of an emergency vehicle giving warning?
Did the autonomous vehicle move into the path of the emergency vehicle? Did it simply stop and fail to clear the intersection? I can't find any video or explanation of the incident so I think "could have" is the correct grammer.
What information do you have that makes you so sure of how the situation played out?