"The vehicle and the test driver "believed the bus would slow or allow the Google (autonomous vehicle) to continue.""
This sounds like a very strong assumption. When was the last time you saw a bus slow down for a car or anything much? There's a reason "Fuck you I'm a bus" is a meme.
Since the light had just turned green, the assumption was probably that the bus would cease accelerating long enough for the Google car to get around the obstacle, not that the bus driver would hit the brakes.
This sounds like a very strong assumption. When was the last time you saw a bus slow down for a car or anything much? There's a reason "Fuck you I'm a bus" is a meme.