It's hard to keep that mile of wire from being pinched.
I remember how the highway authority here in Punjab had embedded blinking lights into the road's surface, over some stretches of road, to help drivers during our foggy winters. A few days after the lights went in, they were dug out and stolen. So new ones were put in. Gone again. New lights. Gone again. Finally the highway authority gave up and left the citizenry to its fate.
In the beginning, they had metal guards but they kept getting stolen. Then they had concrete guards with a metal wire skeleton. Those covers got smashed and the metal wires taken out of them. Now they just have concrete guards but people smash them anyway.
The police and highway patrol have bigger problems and you'd need to stake out long stretches of road indefinitely, pretty much.
Also, making an example of convicted criminals doesn't work. I'd assume thieves risking life and limb to yank LEDs and cable from the middle of a highway in the dark are desperate (and probably poor) enough not to care about precedents.