Spokesman Ross Lamont said the workers, following an internal investigation, were determined to have violated the company's code of conduct as it pertains to email and Internet use.
"It wasn't like this would catch any of the individuals by surprise," said Lamont.
"None of the information that we're dealing with here is business-related. There are no trade secrets, and absolutely no impact on operations, on security, on safety. It was just inappropriate behaviour."
The plant, on the shores of Lake Huron near Kincardine, southwest of Owen Sound, has about 3,800 employees, plus some 2,000 working on contract among them construction workers, electricians, pipefitters and other trades.
All of those dismissed were contract workers.
Lamont said a few isolated code violations triggered more widespread monitoring of workers' Internet use.
"Any significant company has some monitoring of their systems," he said. "We're not confirming numbers, but it's significant enough for it to be alarming."
One fired worker who spoke to the Star on the condition of anonymity said his dismissal took him "completely by surprise."
"It's just bizarre," said the former employee, a 20-year veteran of the plant, about three hours northwest of Toronto.
"I feel like I've been left in the dark. I was given no explanation for my dismissal."
He acknowledged that some employees had been reprimanded in the past and some even received three-day suspensions for inappropriate Internet use, but says he was never warned personally.
Bruce Power's code of conduct states that the company has the ability to monitor email, Internet and file sharing and that "inappropriate use, particularly usage that interferes with business processes or puts a strain on business resources, is unacceptable."
The code lists chain letters, computer games, storing of personal documents and pictures, visiting chat groups, gambling sites and personal share trading sites as examples of inappropriate use.
A contract employee still working at Bruce Power told the Star he has frequently witnessed people watching videos and sharing email photos and jokes brought into work on memory sticks, to the point where the company's Internet servers were being overtaxed by the added traffic.
"You walk through any of the offices where the engineers and everybody are, they're just sitting there, half the time they're watching Family Guy on the Internet," he said.
Lamont said all employees, including contract workers, are required to read and understand the company's code of conduct.
Labour lawyer Howard Levitt says it is "entirely legal" for employers to monitor their employees' actions online.
"It's their equipment, so there's not an expectation of privacy," he said.
John Oesch, a professor at the University of Toronto's Rotman School of Management specializing in organizational justice, said he's never heard of a situation where this many people were fired at once.
But if employees were aware of company policies and appropriate warnings were given, he said, the dismissals seem fair.
"Most companies don't mind if you send a few emails, but if you're surfing the Net when you're supposed to be working or you're using emails for the purpose of something more than just a little bit of personal business, this is outside the policies and procedures of most large companies," Oesch said.