Liberal sources say Mississauga Mayor Hazel McCallion and Oakville's Rob Burton top the party's list of witnesses to be called before the justice committee, which will resume hearings Thursday.
The Liberals want the mayors and leaders of citizen activist groups to talk about the extent of local opposition to the gas-fired generating stations.
The Progressive Conservatives plan to call former energy minister Chris Bentley and Peter Wallace, the secretary of cabinet, in addition to former House of Commons speaker Peter Milliken.
The New Democrats want to call Jamison Steeve, Dalton McGuinty's former principal secretary along with energy experts.
Each party has been asked to submit a list of its first five witnesses to be called before the committee, which had its mandate broadened to examine all aspects of the cancelled gas plants.
The Tories also plan to call McGuinty and his successor, Kathleen Wynne, who was Liberal campaign co-chair when the Mississauga plant was halted in mid-construction.
Wynne has said she would be willing to appear before the committee and promised to release all the documents and other information the opposition parties request.
Earlier Tuesday, the Liberals escaped one of two contempt motions over the release of documents on cancelled gas plants when Speaker Dave Levac ruled they did not intentionally mislead the legislature.
It's clear then-energy minister Chris Bentley and other Liberal cabinet ministers were wrong last September to repeatedly insist all the gas plant documents had been released, when another 20,000 pages turned up in October, said Levac.
"While this sequence of events certainly demonstrates that some statements were incorrect when they were made, I accept that they were believed to be true at the time, not made with the intention of misleading the house," Levac said in his ruling.
"There is no evidence before me that would support a contrary opinion. I find that a prima facie case of contempt on the basis that a member has deliberately misled the house has not been established."
The Progressive Conservatives said the Liberals got off on a "technicality" because it's very difficult to prove a member has misled the legislature on purpose.
"They did mislead the house, but the threshold for proving that they intentionally misled the house is very, very high and has only been met a couple times in parliamentary history," said PC house leader Jim Wilson.
The Tories filed two contempt motions against the Liberals last fall — one for claiming all the gas plant documents had been released and the other for refusing to comply with a committee request to release the documents in the first place.
Both motions died when McGuinty prorogued the legislature Oct. 15 and announced his retirement, but were refiled by the Opposition when the house resumed sitting last month with Wynne in the premier's chair.
The justice committee will still investigate the original contempt motion regarding the release of the gas plant documents, where the Speaker had ruled last fall that there was a "prima facie breach of privilege."
The Tories and New Democrats believe the cost of the gas plant cancellations will be much higher than the $230 million the Liberals claim, and are convinced there are still more documents that have not been made public.
Wynne has admitted cancelling the gas plants was a political decision by the Liberal campaign team.