Line workers are being told they have a strong case for proving they are employees, not contractors, and could be in for a windfall.
They are preparing a class action against Chorus subcontractor Visionstream, saying the company's system is driving them to bankruptcy.
Line workers say they feel bullied and exploited.
Visionstream pays a set-price for each job, which workers said was well below what it should be.
Some weeks they worked 60 hours but did not earn enough to cover their costs. They could even have pay deducted if there are any problems with their work down the line.
At the same time, their contracts stipulated they be available from 7 in the morning, until 7 at night, seven days a week.
A worker - who was leaving the industry in his 50s because of Visionstream - painted a grim picture.
"I have hatred. I find them bullies. No heart, no soul, no feelings, no sense of decency or values. As far as I'm concerned, they've destroyed me."
Law firm Shine Lawyers suspected thousands of workers could be owed money and encouraged them to come forward to join the action.
Employment lawyer Barbara Buckett said it was a strong case.
"They're wearing Chorus livery, they're directed where to work, their work is allocated, and it's controlled by Chorus," she said.
"I think it's got legs in it."
But she added that the devil would be in the detail.
"I think that the real issue's going to come back to what we call the fundamental legal test - whether they're free to go and work somewhere else.
"It looks as though they're not."
Another employment lawyer Danny Gelb agreed the line workers had a strong case.
He said their lack of control over hours worked was an argument for being classed as employees.
But Mr Gelb said they could hypothetically earn more or less depending on how fast they completed a job, which was an argument for being contractors.
He said if they proved themselves to be employees, they could be in for a windfall.
"Potentially holiday pay ... each worker's entitled to four weeks paid holiday pay each year, whereas a contractor's not entitled to any holiday pay.
"As a contractor, there's no minimum wage as such - but being an employee, an employer must pay minimum wage."
The telecommunication's organiser for E tū union, Joe Gallagher, said members were keen to join the class action.
But he said many were scared to come forward - despite being in dire situations.
"Some of these guys can work 225 hours a month, and the primary contractor can deduct money from their account, some of them can end up with $80 a month.
"They invest in all this equipment on these promises of growing a business, but it doesn't materialise. This guy I was talking to is [also] working as a chef in a restaurant."
Chorus, which contracted Visionstream, said it heard the contractors woes, and separate complaints made to the Labour Inspectorate.
It was reviewing its contracting model and said changes were likely.
"It's in everybody's best interests that people feel like they're getting a fair go. We want a highly engaged and highly skilled workforce.
"Without meaning to pre-empt the probable outcomes of the independent review that we've commissioned, I think we can probably anticipate that there's likely to be some structural changes."
Visionstream had not responded to repeated requests for comment.