people would be shocked with how little is included in the city's/utility's master plans. there is vary rarely a professional working on those projects out in the field, and the city/utility isn't responsible to anyone but themselves, so it doesn't matter if they get it wrong.
its pretty much only stuff they installed. and its certainly not everything they installed. pretty much any big project is going to uncover something that shouldn't be there, or is in the completely wrong area.
here in atlanta they were boring and pushing thru some gas pipe. it went thru some old lady's basement. it wasn't discovered until the lady died and they were trying to sell the house. the pipe was supposed to be under the street like 30 feet from that location.
another time they cut the emergency line from a military base back to DC. when it went dark they scrambled jets ready for nuclear war.
there were issues up in knoxville with the baseball stadium because of unmarked utilities causing delays.
we had a project where there was 5 foot storm line running under our property. it was supposed to be the next lot over.
another one had a buried power line that no one claimed until it was cut.
another one had buried pipe big enough for someone to walk in that went more than 40 miles to a military airbase. airbase vehemently denied for months it was there at all, or if it was theirs. base didn't know it was there, and didn't believe us until the GC stuck a guy on an ATV up the pipe and had him pop out on the airbase. he had coordinated with the commander before hand to make sure his guy didn't get shot. less than a week later the airbase was filling those 40 miles with concrete and rubble. never did find out what it was for.