Answer: First thing you need to do is check with the utility company to make sure they don't have any requirements or prohibitions. They usually have an easement around their utility boxes into which you may or may not be allowed to encroach. They will also be able to give you some guidance as to what types of bushes and trees would not be allowed due to root systems interfering with underground utility routes and trunks and branches making it difficult for service personnel to get to the utility box.
After you do that, you might consider installing lattice to surround the utility box -- leave clearance for the utility personnel to get to the box -- and then plant something like morning glory, trumpet vine, or jasmine so that it grows on the lattice and hides the utility box.
Hope this helps.
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