Wirelessly posted (BlackBerry8530/5.0.0.1030 Profile/MIDP-2.1 Configuration/CLDC-1.1 VendorID/417)

You can certainly ask, but a lot may depend on how the Canadian law is written. You might ask AC if they can mark the two tickets as "conjunction tickets," and whether doing so would reduce the taxes. (Such a strategy, if doable, would eliminate the UK APD on transits via the UK, for example.)