The Cruise car failed to yield, continued at a green light, and was struck by the fire truck. So presumably it did not detect the truck.
It is sad that automated cars are being asked to detect emergency vehicles at all.
A system that signals the location of any actively flashing vehicles to all nearby automated cars is technically achievable. It should have been one of the first steps in the development of any of this technology.
Unfortunately it requires careful coordination between many different entities so it hasn't happened.
Edit: Rarely have I had a comment so misinterpreted. I am not excusing Cruise in any way. This is a major design failure for the entire industry.
For clarity, automated cars should be required to have a rock-solid radio-based system that is aware of the position of any nearby emergency vehicle.
All emergency vehicles should have a transponder to signal their location to automated cars.
There's no reason to be relying on visual detection of flashing lights for a fire truck. A fire truck costs most of a million dollars and a transponder is not an expensive requirement.
There should be a standard for radio frequency announcement before automated cars are rolled out and there is not.