Any contractor who digs, trenches, bores, drives stakes or posts, or installs irrigation can hit an underground line. Gas, water, power, fiber and sewer strikes can be costly and, with gas, dangerous. Many contractor GL policies handle this exposure with an underground exclusion or a warranty that coverage applies only if the contractor called the utility locate service before digging.
In most of the US that's 811. The policy wording may require the call, waiting the required time, and keeping proof.
The short version
If the policy has an underground warranty, the 811 ticket is part of the client's coverage. No ticket, no coverage for that strike, even if the lines were marked wrong.