Why would anyone even consider using CN trackage to get from Calgary to Edmonton for passenger travel? Ok, maybe VIA would, since they seem to have an unhealthy obsession with using CN no matter how much grief CN sends their way. A lot of the money that VIA got recently for capital spending is going into restoring sidings that CN took out or extending others. It's kind of amusing that in southern Ontario VIA service always improves once someone other CN owns the tracks - it doesn't matter who, be it VIA themselves, GO Transit or a shortline (or even CP on its residual tracks, notably Smiths Falls to Brockville) - all that matters is that CN not own it. Around Ottawa for example CN has abandoned pretty much everything so the track to Montreal is now owned by VIA, as is most of the track to Smiths Falls. CN, having (re)acquired Ottawa Central, now actually has to run at night from Ottawa to Montreal.
Anyway, how do you figure it would take 10 hours by way of the CP tracks? That's an average speed of something like 30 km/h.
At any rate, VIA is holding the property in downtown Calgary just in case. Similarly, they hold abandoned CP property in the Ottawa-area for a future HSR line to Montreal.