There are particular concerns about the numbers of sub-contractors doing the work.
Mr McWatt said there have been "thousands" of sites around the city, and at one point more than 30 sub-contracting firms on the job.
He said it seemed the apparent haste with which Government wanted the broadband rollout completed meant there were not enough skilled workers.
The council started to become aware of issues late last year and has since kept accurate figures, showing the work is accelerating and the problems increasing.
From November 2011 to July, he said, there had been 25 kilometres of work as the companies laid fibre optic cable for their services.
There had been 119 "strikes or events", two of which led to stop-work notices being issued by the council.
In the five months since July 1 there had been 28km of work, with 130 incidents, including three which required work to stop.
As well as the physical threats to infrastructure, streets and footpaths supposed to be restored to their previous state have in places been left with holes, "wrecked" as one councillor put it, and "messy" as described by another.
The companies have been under instructions in contracts to clear the CBD of broadband infrastructure work in time for the Christmas rush, and also to keep out of sight as thousands invade the inner city at Art Deco Weekend in February.
Major operator Unison used mainly its associated Unison Contracting and its staff for its work, which started two years ago and was all but complete, said community relations manager Danny Gough.
The company had tried to work as closely as possible with the council and other facilities companies to minimise issues, and he conceded there had been some minor but expected issues which had been dealt with.
"We're pretty much out of the CBD now," Mr Gough said, explaining the company has unrelated work to do around the new Farmers Trading site, and a fault repair further south in Hastings St.
Chorus started work on its infrastructure later and has been working extensively throughout the city in recent weeks.