Where I live, "meeting of the minds" is necessary for a contract. Written or not. In this case, that meeting didn't happen. Due to the bullshit generator employed by Air Canada.
So there was no contract but a consumed flight. The court has to retroactively figure out a reasonable contract in such cases. That Air Canada couldn't just apply the reduced rate once they learned of their wrong communication marks them as incredibly petty.
This chatbot merely said something was possible, no legally binding agreement occured.