Strategically, this a move that I think shows to the Canadian labour bloc, that actions like what the Liberal minister did to the rail workers don't go without consequences. Singh can harp on, consoling and hugging union leaders if he wants but rescinding the agreement is one big step above just talk that is within the NDP's power.
It definitly has a Catch 22, because I dont want to see a snap election, I think the conservitives have too much a chance of forming a government, and as rough as the Liberals can be, the conservitives would be far worse... but we can't have the NDP just being unwavering support for the Liberals.