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That seems quite likely to me given just how much bandwidth would be required if every street light had a live video feed.
I would also imagine cameras are pointing downwards to detect cars passing on the section of road they illuminate, average speed being calculated from the length time it takes for a vehicle to pass underneath; it doesn't have to be that accurate.
The idea that Suffolk Police will be tapping in to the lights to add speeding ticket printers seems fanciful to me. That appears to me to be more scaremongering than credible fear. Had there been more of a technical review of the hardware used and its capabilities we could all have perhaps been better placed to assess it.