at work here, we just take them down and into the streetlight dumpster they go. where from there, I have no idea. I throw away good lights all the time and it kills me but its part of my job and I don't want to get in trouble by taking all the lights I throw away.
@ gailgrove A lady in charge of the main warehouse at Duquesne Light in Pittsburgh told me four years ago that they don't accept streetlights at the warehouse anymore and that they're loaded up into box cars. The lights are scrapped too.