No, that's just a strategic move to keep the NDP down. Grits have been doing this with social democratic third parties for nearly a century, it ain't new. Most recently, Paul Martin campaigned with then CAW-chief Buzz Hargrove in 2004/6.
It's not just the union speech, it's Trudeau capitalizing "Labour" throughout his speech, as well as making Liberal party membership free and stating he wants to transform the party into a "movement".
It can only be a movement if it becomes the "Labour" party (ie: the Labour movement).
At least that's what has happened in Britain, Australia and New Zealand.
That would make no sense. They're riding high right now, why rock the boat? Canada already has a Social Democratic Party, and they've already poached most of the votes from them that they can. It would be a dumb move.