If an ostensibly normal car were to block an emergency response, would its occupants be off the hook if they all denied having driven the vehicle to its current location, and said they have no ability to move it out of the way? I doubt it. They would be at the very least charged with something.

The same thing should go for alleged robotaxis—“But we don't control the car we're sitting inside of!”... not the city's problem. The car you were in was blocking an emergency response.

Would this be unfair? Yes it would. Would this make people fearful of using robotaxis? Absolutely yes it would. And would that put economic pressure on the robotaxi operators to fix these issues as fast as possible? Damn right it would.