Fourteen of them lost their lives.
A coroner's report in 2013 said public health authorities did not have the proper tools to combat the outbreak, which came 16 years after similar cases in 1996 prompted calls for change.
Catherine Rudel-Tessier said not enough was done to bring about that improvement.
Lawyer Jean-Pierre Menard said Thursday he believes he will get the green light to proceed against local health authorities, the provincial Health Department and a teachers' union that owned the building where the disease originated in a cooling tower.
The 2012 epidemic, Menard said, "was one of the biggest in modern times given the number of victims and how long it lasted."
"The victims have a chance of being compensated," he told a news conference. "We can't guarantee it (but) there are a certain number of facts that are extremely telling."
The request is based primarily on the argument that health authorities did not take the necessary steps to avoid the outbreak, with Menard saying they were slow to respond and that their management of the crisis was "chaotic and disorganized."
It was filed in Quebec Superior Court on Wednesday by Solange Allen, whose husband died in the outbreak.
"I would have liked some empathy from public health officials," Allen told the news conference.
She said the crisis never should have occurred.
"That's what's annoying, that's what we can't accept. This can't be allowed to happen again."
Menard said the suit, if it proceeds, could total as much as $6 million.
A decision is expected in August.
Legionnaires' disease is contracted by breathing in small droplets of water contaminated with bacteria. Symptoms include coughs, fever, chills and respiratory problems.
The deadly bacteria grows in the stagnant water of cooling systems and spreads in little droplets through air conditioning.
Heavy smokers and people with weak immune systems are most at risk of catching the disease, which is not contagious and cannot be transmitted from one person to another. It presents little or no risk to most people, although elderly people are more vulnerable.