That’s interesting, thanks for posting. Our mains electricity comes from an overhead pole located about 15m from the studio building, I believe it’s at 7200v and there’s a distribution transformer on the pole supplying our house and studio (2 separate buildings).
There is a railway line about 100m away but it’s not an electrified line.
I do suspect the interference on pickups may be related to the proximity of the transformer, but it’s HF buzz, not a 50hz hum, and moving the guitar around doesn’t affect the interference.
I now have the Furman power conditioner, we’ll see if that helps.