about this report and related issues
Back of the envelope math:
According to The Scientific American, in 2010 there were 200,000 miles of high voltage power lines and 5,500,000 miles of local distribution lines in the US.
According to Columbia Telecommunications Engineering, best-case aerial (utility pole) fiber optic construction costs are $25,000 per mile. Worst case buried cable costs are $400,000 per mile.
Relying on that same source (and some personal knowledge) about which of those two is more common, the average cost will be much closer to the first than the second. Let's take the $100,000 per mile worst-case aerial amount as an average.
Toss in big cross-country lines, assuming double the cost per mile. This gives us a cost of $590 billion dollars to run fiber optic cable to everywhere that had power lines in 2010.
(I invite better sources or anything that would refine this calculation)