If you have a map of all utility poles you could probably just avoid every straight line between any of them within some reasonable distance of eachother.
it's an approximation of dangerous areas, catenary curves are more accurate than straight lines but you don't know the length of the cable so you don't know the droop height.
All cables? Everywhere in the entire country? Accurate to the centimeter level and updated on the hour?
Edit: This was flippant, but the real issues are: any map you get will be incomplete and obsolete almost immediately and cables move and sway in the breeze.
Google sell maps of things like this from street view data.