What kind of video inputs does the 2001 monitor have? Your 2011 iMac has a Thunderbolt output port which is backward compatible to the MiniDisplayPort. Whether it's Canadian or Australian shouldn't matter as long as the Canadian monitor can operate on 240 V since Canadian power like the US is 120 V.
If I am only using it as a secondary monitor and all the power is actually coming through the iMac, will it harm the iMac if the Canadian power is 120V??