If I recall correctly from my Catholic reading, stealing can be mortal or venial, depending on how much the item stolen is. For instance, while stealing a car might be considered a mortal sin, stealing a candy bar is only a venial sin. So, if copper is not that expensive (don't know if it is or not), then what these theives did would not merit hell.
As I understand it, if you steal a day's wages, that would be a mortal sin. But what if it's city property? What are a days' wages for the city that owns the infrastructure?
Is stealing thousands of dollars worth of copper (and doing tens of thousands worth of damage) a trivial theft, or a serious theft?
I'm not a theologian, but I'd have to say it's a serious (grave) matter. After all, you're talking about destroying public property, instead of just one man's. How many people lost power because of this? Did anyone commit a sin because of the outage?
Did anyone lose a days' wages? (Telecommuters and contract workers, for example) Did anyone DIE (besides the thieves)? And if no innocent people died, was that because of luck, or was it actually impossible?
Matthew