I read your post with interest as I am undergoing a similar situation in SC. Our local utility company has recently decided to selectively maintain their easements based on what I can only assume is their opinion of your neighborhood. Upscale neighborhoods get selective trimming, if anything, with trees and shrubbery allowed in and over the lines.
In rural areas, like where I live, they have decided to implement a new clear cut to the ground 'policy' (which they liberally cite, but will not provide you) for their right of ways. I unfortunately have three ROWs on my property: one in the road ROW which traverses the front of the house; one on the property line; and one that cuts off an acre from the rest of the property (and provides service to an adjacent property - which actually also has another distribution line coming in from their street). I about had a heart attack when I came home from work and found a 20' wide swatch completely clear cut to the ground! This included the 85 cedar bushes that formed the living fence along one of the property lines and were about 6' below the line (the power line was put in directly over them). They took all the cedar with them and left behind a rutted out, debris strewn mess. I had to pay to clean it up and construct a 250 foot long fence (it would have been cedar, but...). They come back every 9 to 12 months to cut down wider and wider areas around the line - outside of the apparent 10' easement. I feel like I am being harrassed - particularly when they have not trimmed their line only one block over in over 5 years! I have asked for their policy, asked why the ROW maintenance is implemented inconsistently, asked them to repair the road, asked for help on the erosion, and asked them to clean up the mess they left. They were very rude and quite honestly I am afraid to ask any more as are other people in the neighborhood. I was told that not only were they not going to clean up, but they were going to return and herbicide the line! And so a few days later, every blade of grass that I had tried so hard to get to grow in this mess of a ROW was dead as were the bushes that were outside of the line where the herbicide made contact. I have found you cannot win with logic or facts; I have been very polite in all my interactions with them. My neighbor threatened to kill them if they touched his trees and guess what, they are still there!
I obviously have no rights at all to put anything on or do anything with theis ROW property that I have to pay taxes on. I have requested a copy of the easements on my property from them (the lines were there when I purchased the place) and they said they don't know what I was talking about and would not provide them to me. The easements are not shown on the deed or any paperwork for my land. I had no problem with this as long as we were allowed to keep our landscaping - we maintained the lines very well, so that they were attractive and not the ugly property value reducing eyesores they are now. I totally sympathize with your plight - it seems like our ROWs have actually become the property of the electrical utility company while we pay their taxes for them. This seems to be taking and beyond the intent of the easement (whereever they heck it is!!).
I do not know what I can do, other than pay them the $10/foot they want to install at least one of the lines underground.