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used with similar systems for city transit. It's my understanding that the transit system differs from the emergency system in that it's only activated when the bus is behind schedule and as you correctly guessed, does not turn red lights green, but rather holds the green lights until the bus passes. The system would also likely only work in the areas participating in the network they were originally implemented in. Assuming you bought the buses local, it might be fun to throw 12V to one and give it a go. FWIW, I emailed my buddy to ask if there was anyway the city could identify who and when the system was activated. 
WARNING: I lack industry backing
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