I'm not an EE but I agree.
The $15 million a mile quote smells like BS, however. Maybe in the city or the interior suburbs but how much does it cost to run a ditch digger out in the exurbs where the tree problem is the most acute?
Hell, hire the legions of unemployed and give them shovels. Kill 2 birds with one stone. /pissed off sarcasm.
Seriously, I'd like to have someone break down $15 million a mile. That's $2840 a FOOT to dig a ditch and lay wire. I smell BS.
Rant over.
15 million is probably a low estimate. Underground might be fine and dandy in your subdivision, but transmission lines are another thing. No way are you going through mountains and valleys underground