Shock news. Smart streetlights *already* exist
In fact I believe the whole of the Motorway and A road network use them.
Other countries power their street lights off a separate network but UK practice is to hang local street lights off of the nearest house supply, making control through the mains (used in other countries) unworkable.
What are they used for? So section of Mway can be gradually dimmed down when there's no one actually on them at 3am on midweeks. They can also report bulb or *gear" failure (or even impending failure) without waiting for some member of the public to phone in saying "Do you know...?"
The best systems fail safe. If the control fails it fails with light full on. then it's under the control of either a timer or photocell in the lamp.
And if councils insist on hooking this up to other systems where there is a way in there's someone likely to use it, if only for the s**t and the giggles.