palmetto,
I work for one, know little. It is no easy job. money to be made, but the utilities are like everyone, one day money, next day broke. You as a contractor will be first to go.
If you do get lucky, you will need much heavy equipment. some lines are pretty overgrown. may want clear cut. god knows what you will find under those lines. Many used as dumping ground. Hard on equipment.
Many different aspects to what you request. Line clearance (tree trimming only) right of way clearing (clearing out old growth) ROW mowing (just mowing grass) all done on different priority. If you have storm season, they will want tree trimming pretty regular. all the rest are pretty dependent on department budgets. Some company's better at this than others.
Heavyduty correct, search and ask for right of way department. They can point you to the right people. Have insurance, bonding, and price list in hand. They will want all, and why you are better than who they are using.
Plenty of $$ there if they turn loose of it. Good luck.