You've marked the area in white paint where the new guardrail is to be installed. You've called your state utility marking service and wait the required time before sending a crew out to begin work. The supervisor mentions a fiber optic cable marker on site and wonders why the tickets have come back clear. Obviously, you can't proceed until you've double checked these data.
Who would be responsible for cutting a fiber optic cable in this scenario? Even if you didn't know, the test is often "should you have known?" This test requires your site supervisors to check site plats for any utility easements, any visible marking signs within several hundred feet of your site, and interview the marking crew to request specific concerns.
Double check any laterals for water and sewer, is electrical service buried or overhead? How about private utilities - any lighting or signage on site still work?
The site supervisor needs to stake out any areas where extra caution is needed. Great due diligence saves time and money in the long run.
Fencing contractors run into the problem of unmarked or improperly marked utilities constantly. They bore holes to utility depth exactly where utilities turn into the site. They must bore holes every eight feet. The most professional fence installers hit phone and power lines. The key is to document your due diligence.
Take pictures of all utility markings before you dig. If you have any question whether the site has been mismarked or a specific utility has not been marked, take pictures of the markings currently on site, then call for the remark to document the difference.
The key is to have a high level of certainty that you know where the utilities are and they are properly marked. Next, document the efforts made to assure these conditions. Then dig, bore or plunge with confidence, and the knowledge you have done your best to avoid utility interruptions.