I agree that getting rockets back from power lines is stupid (Who doesn't). I've played alot with High Voltage. It's quick, it's scary, and you can only make ONE mistake. Just one. And the worst part is, it jumps through thin air.
The general danger is such... Anything that looks like an electrical insulator, isn't at 70,000 volts. A piece of wood at 70,000 volts will happily carry enough current to kill you. This is why power lines are hung from giant hunks of ceramic.
I should point out that some weekend in college (We're cool kids, eh!) my friends and I lost a rocket in the power lines right smack across a road. The rocket was hanging low enough that a tall truck (Or the campus buses!) would have brushed it, causing an instant problem. Panicking, we started throwing rocks at the nosecone to try to flip it down while directing taller vehicles around the dangling rocket. A safer solution than going up to grab it, but still kind of stupid. We eventually got it down, but we all kind of wondered afterward if the power company REALLY would have charged us.
Well, I called the power company and they told us that they are required to remove things dangling from power lines. Essentially, if we had called them, they would have had an emergency crew out there in under an hour to take it off, without charging us. We probably would have payed the guys everything in our pockets in thanks, but alas...
Just call the company. If they want to charge you for it, So be it. Things dangling down from power lines are just asking for someone, other than you, to try to get it down. Not to mention, its easier to touch something dangling down. Is it really worth knowing that some curious (proboably drunk, in our case) people tried to poke down your rocket and died?