Just thought of another possibility: typically the easments along property lines are intended for local service utilities. The line you hav obviously is a larger transmission line. It may have a sepeate easement that was taken at a different time, and the title company missed this seperate easement.
Good luck with this. Have you consideder a shed that is small enough to not need a permit? If that's allowed in your area that might avoid the whole issue entirely. It could be built on PT skids, or on non-permanent footings, and be not be considered "permenent" . Tou can do that in my area and put it in an easement. Worst case is the utility needs to work in the easement and the shed needs to get moved. Not ideal, but might be practcal.