Well, nothing, actually.
The Liberal Party has always been a centrist (and opportunistic) party, slightly to the left of the Progressive Conservative Party. The fact that the latest incarnation of the Conservative Party has moved to the right does not make the Liberals progressive. Indeed, if anything, the Liberals under Iggy have moved to the right into (and past) the spot held by the old Progressive Conservatives.
As for the Greens, they are simply a recognition that broader support for environmentalism has created a spot for a right wing environmental party that recognizes that without an environment there can be no profits and that there are profits to be made from environmentalism. But their solutions are clearly capitalistic and not progressive.
The fact is that Canada has only one mainstream progressive political party. It is the party that has always been the political wing of the progressive movements, including the environmental movement. And, of course, that party, with it's own inherent problems from time to time, is the New Democratic Party.