The government announcement came just two days before a deadline that had been set by Kinder Morgan.
A second, smaller protest happened in Whistler on the same subject; protesters there were hoping to catch the eye of federal Finance Minster Bill Morneau who is in town for the G7 Summit.
The Trans Mountain expansion is projected to lead to a tanker traffic balloon from about 60 to more than 400 vessels annually as the pipeline flow increases from 300,000 to 890,000 barrels per day.
"We're fighting for your jobs, for your resources and the livelihoods of hundreds of thousands of hard-working people here in Fort McMurray, across Alberta and across Canada", she said. Canada has the world's third largest oil reserves but 99% of its exports now go to refiners in the USA, where limits on pipeline and refinery capacity mean Canadian oil sells at a discount.
"We still have no guarantee of this project proceeding", he said. Weve agreed to a fair price for our shareholders and weve found a way forward for this national interest project.. If built, it will triple the amount of oil flowing from Alberta's tar sands to the coast of British Columbia.
After the sale is complete - anticipated this August - the federal government will pick up the construction before selling it to a new "long-term" owner.
Blaney also said that the buyout doesn't align with promises made by the Liberal government.
Alberta Premier Rachel Notley cheered the news of the purchase on Twitter.
Conservatives both federally and provincially were less jovial about the news.
As the Trudeau government prepares to take over the controversial $7.4-billion Trans Mountain Pipeline expansion, project management experts say it is critical that government oversight is handled properly.
And so the federal government is going to build it, assume the risks with taxpayer money and somehow deal with the continuing protests, including the potential for violence and for citizen arrests.
"That multiplied over 365 days a year, you get a pretty good idea of the $18 to $20 billion dollar hit the Canadian economy is taking because of protests and people blocking pipelines in this country", he said. "Not in anyone's universe", May said on CTV's Question Period.
Industry observers say that until jurisdictional and ownership issues are resolved, the Canadian government will have difficulty attracting a serious buyer. With the federal takeover, the group is hopeful that will change.
A new project proponent would be eligible for financial support for additional costs caused by the discriminatory and unjustified actions of a province or municipality in an attempt to delay or obstruct the expansion, the government said.
Opposition leader Jason Kenney issued his own statement that took aim at Prime Minister Justin Trudeau. A government commitment, she said, could "ensure women, Indigenous people, and apprentices get work", in the trades.