Every state has their own laws concerning utility locates and responsible parties. The only way to really know what is legal and who is responsible is to read the laws in the state that you are working in or hire an attorney to interpret them for you. I have very little to do with locates since I only work aerial plant but I do have enough experience to notice things like outbuilding that have lights, septic tanks, water meter pits, lawn sprinklers, gas grills, wells, etc. They all give you clues as to where there might be buried utilities.
40 years ago yards were pretty clean as far as underground utilities. All you had was gas and phone and maybe electric and/or cable TV. But now there are manicured yards, electric dog fences, natural gas grills, multiple communication lines, electric in all most all lawn sheds and sometimes phone and natural gas. A lot of these lines are buried by the home owner at less than the recommended depth.
