One criticism I'd have with that study is that it seems to presume that hourly demand for heat would be similar between heat pumps and gas furnaces, but that's not a given because they work differently. With a gas furnace, you might set the temperature back at night or during the day to save energy, and then it comes on full blast in the morning or evening to make up the temperature, leading to the huge spikes in those times.
Heat pumps don't really work that way, and there usually isn't much benefit to setting the temperature back for shorter periods of time, nor do they have huge peak power consumption. So the usage would be much smoother (and if anything, higher at night when the temperatures are colder). So if a region was heating with heat pumps, the peaks would likely be a fair bit lower.
I've monitored my heat pumps' electricity usage when I've been away for several weeks at a time (which removes virtually all non-heating electrical usage), and the flatness of the curve is crazy:
