From what I gather this isn't the case. The signal resets if the decibel measured go past 85. It's unfortunately probably very easy to abuse, and some troll will.

Also, here's a video made by the Mumbai police: https://www.youtube.com/watch?v=KIgKvUPXeq4

Not sure that applies here since one person honking won't gain them any advantage. Very possibly a tragedy of some other sort.

I imagine that this might be a self-solving problem.

A mob of angry people who now have another 90 seconds on their hands would likely deter all but the most foolhardy trolls.

No, because 1 person honking won't go over the loudness threshold.

Yes and it's worse than that because it's kindergarten collective punishment. It doesn't consider an increase in property damage and deaths from people afraid to honk or who's vehicle owners will remove their horns, thinking it will lead to increased productivity. Instead, the police need to be less corrupt and enforce a ban on aggressive honking, and correct behavior to use the horn only in emergencies. It seems like another bureaucratic, half-assed, lazy, counterproductive panacea rather than fixing policing.

A more precise but more expensive method would be to use phase array mics with license plate recognition cameras and just create a nominal fine.

It goes off a decibel Meyer that is triggered by multiple honks at the same time, as per the video.