I have not heard about this species occuring in Alberta before and it is not in John Acorns, Ladybirds of Alberta. Is this a common species there?

It was introduced to Quebec in the late 1960's and has been spreading west and south ever since - it's at least as far west as the Great Lakes by now, perhaps farther. So it's definitely headed towards Alberta, if it's not already there. It's also sold for biocontrol and could be locally released anywhere without creating established populations.

I've run the Rees et al. key to Nearctic coccinellid larvae(1) several times on this larva. The pointed terminal projection on A9, along with pattern and black-and-white color, always lead to P. 14-punctata and Calvia 14-guttata. Calvia has large conical spines - senti - on every abdominal segment, including laterally. This larva does have raised dorsal and dorsolateral projections, but they aren't sharply pointed, and there are no prominent lateral projections. On the 4th abdominal segment of this larva, the dorsal raised areas are pale, not contrasting with the body wall; Calvia's dorsal senti on A4 are black.

Zooming in and sharpening in Photoshop, I think I might see one significant feature that's more like Calvia than Propylea - raised scoli or even senti on the meso- and metanotum. It's hard to tell, though, and Calvia would still have many more senti on the rest of the body.

Maybe this larva is neither Propylea nor Calvia, but in that case it's not in the key either. I don't know what else it could be!