Most of those are utility company owned and require available access. They can and will remove anything that keeps them from access for safety reasons. Plants can be placed as a berm within 8' but don't go too deep as there are plenty of buried wire, some no more then 6" deep. Grasses are usualy best.
They make faux rocks to cover them.
Kimberly I like the idea of faux rocks, can you post a picture & possible tell me where I could get some, I too have the ugly huge green electrical box in my back yard
faux rocks look nice but so expensive