I went and bought a HD-PVR last weekend and this past week after a reinstallation of Windows 7 I have HDTV in Media Center from my Motorola DCT6412 with Shaw.
Everything seems to work fine except for the buggy nature of the DVB-T drivers that make Media Center recognize the HD-PVR. I am able to change channels with the IR blaster on the HD-PVR and recording and pausing work fine.
With the HD-PVR going to be officially supported in Windows 7 when it is released I am happy to finally see HDTV in Media Center in Canada.
Now, if only I could get away from using the set top box altogether.