Eh, they just love using the lines as runways, though normally it's the lower cable/Telcom lines. It's not terribly surprising the little bastards cause problems, especially where trees grow close.
We once heard a big bang in the morning as the power went out. Decided to go for a bike ride and saw the just-fried squirrel at the base of the pole right behind my house.
I've seen a squirrel get electrocuted by a power line with my own eyes. Bright blinding light, bzzzt sound, and later charred squirrel on the ground. Can't be that rare