Among the first on the scene were Rua Roberts, 36, and Kevin Nicholson who were in an Auckland City Mission delivery van when they came across the incident.
"We saw one of the workers lying on his back on the side of the road next to the truck. We dragged him across the road because of the cables - we thought they might drop everywhere."
Mr Nicholson saw the other man on the other side of the truck. His jeans were still on fire so he grabbed a water bottle from their truck and poured it on the man's burning legs.
He then returned to the first man and began CPR while Mr Roberts supported him and watched for traffic. He feared the man was dying in front of him.
"He was pretty much gone. He was pale, really pale."
Others joined them, including physiotherapist Andy McGregor who ran from his clinic across the road with a defibrillator.
"He used it on him. He vomited after the first shock and they continued doing CPR and he came through ... He was on and off a few times there. He'd breathe a little bit and then flat-line."
He said a lot of people tried to help and it definitely gave the men a chance to survive.
Mr McGregor told 3 News he followed the instructions on the defibrillator because he'd never used one before.
"I had a defib kit so I put that on him and followed the instructions and then yeah, it kicked off," he said.
"We kept doing CPR on him and we just kept going until the ambulance arrived."
It was the first time he'd used the machine after being trained by St John to use it only months earlier.
Ryan Prasad, 39, saw one man lying on his side. "He was still burning. I could see smoke and flames coming from him."
The man was lying on his side making groaning sounds as those around him tried to keep him alive.
"They were telling him to keep breathing," Mr Prasad said. The man had bad burns to his legs and hands and his clothes appeared ripped.
The rear left tyre of their truck was burnt as was the grass around it where the electricity earthed.
A spokesperson from Vector Energy, Sandy Hodge, said the men appeared to have been backing a truck with a large structure on the back which hit powerlines.
Vector contractors were sent to the scene immediately to make the area safe, she said.
The matter is being referred to Occupational Safety and Health for an investigation.