Don't know about other parts of the country by here in Indiana if you dig, pierce, or do anything that would or could damage utility infrastructure you can be held liable fore the damages and or be hit with a fine for up to $10,000 and or one year in jail or both if you do not have a locate done before digging or dig after the locate has expired (48 hours here)
From experience I also suggest to take photos of all locates as they might save your butt in court if you do hit something, in at least three times it saved mine.
The first time I was using my back hoe to dig in a sewer line for the plumber as a favor, we had locates done and they came out and painted on the neighbors drives with big arrows "NO UTILITIES" with the arrows pointing toward the property we had to dig in, around here it is common to have not only the primaries but the secondaries and gas all in the same trench, not even including the cable and telephone trunk line which was about 6" off center of the electric.
Well the back hoe did what it was great at, it located them, including a 600 pair telephone trunk, 7.2kv primary and the secondaries to the neighbors house, well we had photos and when we refused to pay both the POCO and Verzion (telco) we were sued, but what they didn't know was we had photos, and I counter sued for the hole in the side of my bucket that happened when I hit the secondaries and primaries, lucky the gas main was about 2' and I had just scraped it in the same pass when I hit the rest, well when I was called up to the bench to tell my side to the judge I showed the court the photos of the locate that was done and the paperwork for when we ordered it, then entered my counter suit the POCOs lawyer jaw just dropped when he saw the photos, and the judge just dropped the POCO's case and ruled the locate company responsible for my bucket (the locate company was own by the POCO then), the neighbors also sued and received a driveway cleaning to remove the paint off their drives, I got a check for $2100.00 for a new bucket (never replaced it) but did get a narrow trench bucket with part of the money.
The cost of the damages they were trying to make us pay was $6800.00 from the POCO, and $1200.00 from the telco, this didn't even include the possible fines or jail time I was facing if I was found guilty of the damages if I didn't have the photos of the locates to which the locate company denied us ever calling in (remember they were owned by the utility) they were also hit with a contempt of court for liying about it.
another one which I had posted photos here on involved a ground rod that hit a gas main that was mis-marked in the locate, they had known that I took photos and never tried to charge us.
So your best defense is to always take photos and document when you call for locates and when you dig.
Just calling for locates may not always be enough.
well photos save our butt and got me money in return