We fix a lot of damage due to GOOGLE FIBER SUBCONTRACTORS.
Best bet is to TEST your irrigation system while the workers are still present on your block to be sure there is no damage. Document any issues with PHOTOS of both the irrigation issue and any tag or paint that indicates that Google fiber was present.
Getting a supervisor over to look at the damage WHILE THE HOLE IS STILL OPEN is your best plan.
If you wait a few weeks or month, it's going to be a lot harder to convince google fiber to pay for the repairs.
Our clients have had good luck getting repairs covered since we take lots of photos and share them with the invoice so there is a pretty good paper/photo trail.