I live 7 km up Burch Mountain. The measurements were taken at 13.3 km.
1) I did take meter reading with a SQL meter during the transition period. My meter readings were taken at N45, S45, W45, E45, and overhead. They all showed a slight decrease in light pollution during the transition. Unfortunately, I only took meter reading during clear nights and from Thanksgiving through President's Day Wenatchee weather is just as awful as Seattle's.
2) The DOT streetlights are VERY BRIGHT and at 4000K. I was coming home last weekend and noticed the significant difference between the county streetlights and WA Department of Transportation streetlights. There are lots of DOT streetlights along the three interchanges and two highways in the immediate vicinity seen directly from Burch Mountain.
3) There has been significant "subdivision" growth up Burch Mt. The county does not have any streetlights, but all my new neighbors from Seattle think ONE porch light is not enough and have taken to stringing up 40 plus lights in from of their homes. That is a significant increase in light since ALL are unshielded.
4) My sky to the east was pretty dark and then suddenly new businesses opened along Highway 97 to the east of me. Now that sky is pretty bright in spite of the fact I am 500 feet above and blocked by a ridge.
5) Wenatchee has lots of ball fields that "spray" and unbelievable amount of light up Burch Mountain. There is a chance that the 2018 reading, the ball field lights were off and on for 2019. That would account for the increase just by itself. Not sure if there is a way to check this at this point.
There is a problem with just ONE observation. I would have given the PUD permission to set up a monitoring station at my house. I do give them credit for attempting the measure the effect of LED streetlights on the night sky.
My take, streetlights are not the problem. It is the private lighting practices that are degrading the night sky, much more than streetlights.