In my area trenchers are close to worthless due to clay soil with lots of complementary ROCKS.
Directional drilling and missles are definitely a superior way to go. A missle can be lined up in a cellar, and punch it's way to a small hole at the water main in less time than it would take to dig a trench, let alone backfill and restore.
A couple years back fiberoptic was drilled all the way from Buffalo to Albany on the Thruway right of way, and the figures to do it were less than half the cost of trench and backfill.
Soil conditions dictate the method of excivation. Laws dictate instant bankruptcy if you don't have a locate, regardless of what you KNOW is in the ground. Fiberoptic has been buried all over America, and clipping one of those will get you a bill for thousands of dollars per minute the cable is out of service. I've lived in this house over 50 years, and I wouldn't dig in my own yard without a locate. Let the utility assume the cost of locate errors, they budget for it. The electric utility here won't even use their own augurs to set new poles cause they know the mapping sucks, they employ contractors to dig pole holes by hand.
