Volcanic Tablelands north of Bishop: winter boondocking?

We are hoping to take a week-long trip in mid-December -- the Geminid meteor shower is on the 13th. The higher-altitude areas of the Eastern Sierra are not going to work -- there is already some snow, and the night-time temperatures get down to the single digits.

So we are looking for some lower-altitude boondocking. I checked with the BLM, and the Volcanic Tablelands north of Bishop are open all year. I see a lot of campsites on Google Earth. But I have a few questions, and I am hoping that some of the rugged folks on this forum can provide some answers.

First, if you have camped on the Tablelands in the winter, how was it?

Second, is there much light pollution from Bishop? (Obviously, the further we get from Bishop, the better, but that means a longer "commute" each day from the campsite to the highway.)

Third, is there a lot of traffic on Casa Diablo Road, which is sort of the main route in and out of the area? If it gets busy, we would just choose a campsite further off the road.

Fourth, looking on Google Earth, there looks to be some sort of a water treatment plant in the Five Bridges area, where Casa Diablo crosses the Owens River. Is that a sewage treatment plant? (I hope not, but it would be good to know what it is.)

Thanks in advance for your advice!