It's understood the Unison worker had been part of a team cordoning off an area where they were to begin work strengthening power poles.
Police believe he had been standing next to a stationary Unison truck when he was crushed by another as it drove by. Colleagues called emergency services and stayed with him until ambulance officers arrived.
"We have interviewed the driver and we are waiting until we can interview the victim," road-policing supervisor Sergeant Kevin Stewart said.
"As far as crashes go, it's not overly involved or serious but the injuries are serious ... when you have got workers using heavy machinery there's always that potential for injury."
Inquiries were set to continue, but it was too early to say if any charges would be laid as a result.
Unison Networks customer relations manager Danny Gough said the company was providing help for its employees who were, "obviously shaken" by the accident.
"We have measures in place to support staff. We are a very close-knit team," he said.
"There are counsellors available to speak with them; obviously our main priority right now is the man, his family and our staff."
Those who witnessed the incident were taken off site and given the option to go home or continue working.
Mr Gough said an internal investigation would shed more light on the situation, but he was thankful to hear the employee was getting the best care possible.
"We are just hopeful that he will make a speedy recovery."
WorkSafe NZ was also conducting inquiries, but could not confirm how long that would take.
Just minutes earlier, a short distance across town at Tainui Reserve, a Regional Council worker was pulled, groaning, from a sheer three-metre drop.
He had been using a handheld weed trimmer to cut long grass next to a Karamu Stream tributary, when he fell awkwardly while climbing up the steep bank.
A Keirunga Rd resident who only wished to be known as Matthew, was alerted to the man's cries and ran to help.
"The woman who lives next door to me blew a whistle and I heard what sounded like groaning so I yelled out and asked if he was okay, he told me he had broken his leg.
"He's done quite a bit of damage, he was in a lot of pain."
Two women walking their dogs in the reserve also came to his aid and rang an ambulance.
Fire trucks from Hastings station and the Havelock North volunteer brigade were called in to lift him on to flat ground.
St John district operations manager Steven Smith said the man was taken to Hawke's Bay Hospital with a fractured leg, where he remained in a stable condition last night.
