Yeah, it's a crazy intersection to begin without adding in emergency vehicles.

I don't have much knowledge of what happens when an emergency vehicle signals that they need to get through an intersection, but it's not like it flips immediately. My guess was more that maybe traffic on Plantation St (or vice-versa) had been waiting for the light and shortly after they received the green a request came in to change so it was only green for a couple of cars and those behind might not have looked or assumed it was still green if there was solar glare or something.