You should first contact the City and have the lines marked if they are underground. Usually high voltage lines are several feet in the ground and lines like cable, telephone can be anywhere from a few inches to 18 inches. Service electric to your home will be 3-4 feet or so. Even if the lines are marked, you should dig with great caution. If above ground, your choice of plants should be ones that will not interfere with the lines as the trees mature or understand that the company charged with keeping the lines clear have the right to prune accordingly. there are cultivars of River Birch that have differing mature heights and widths. While there are cultivars of Bald Cypress, I do not know of any really small statured types. Shawnee Brave is more narrow and upright, but at maturity is still 30+ feet across.