It looks like a backstop, if you follow me, that it's there. It's as you said; it has been made available before but was never used. In the case of some financial crisis, Canada was a mix of great foresight and lucky, in terms of the last major global financial crisis.
China, to me, in terms of understanding the decisions of the Chinese government with respect to their currency, is perhaps less transparent than some of the other trading regimes we've had. Why is it not a backstop? Why make the money available if not for the potential of actually using the money in some crisis?