The worker, believed to have been in his 50s, fell several metres down a "sheer drop", but fortunately was caught up in some large trees and undergrowth after landing.
This prevented him from falling or rolling about seven metres further down a very steep embankment slope into a creek, O'Neill said.
"He was working on the side of the road and slipped down an embankment," O'Neill said.
"He's got some possible back and neck injuries."
Four firefighters from Willowbank Station and four from Dunedin Central Station helped rescue the man - four in the basket and four lifting him to the road.
Firefighters were working in a confined area, with a further drop nearby.
One of the most challenging tasks was to carefully roll the worker, who had fallen face down, into the rescue basket, before lifting him to safety.
St John was also in attendance and ambulance staff gave the man initial pain relief before he was lifted to safety by the FENZ crew.
After he was rescued from the bank, the man was swiftly taken off to hospital to receive further treatment.
"It's just one of the jobs that we do," O'Neill said.
"It's good to get to assist the public and do what we do under trying conditions."