https://tiresize.com/calculator/ has a tab for comparing two sizes, you can put the two sizes in and see the differences, including how much your speedometer will be affected.
The 215/60s are wider and taller than the 2015/55s, which will make your speedometer read about 5% lower than actual (which may make you more likely to speed) and the bigger tires would change your overall gear ratio, and could have some negative impact on acceleration, although I don't know you'd notice it. I can't remember if wider or thinner tires are better in snow
My guess is that the tires would mount ok on the steelies, but I'd be lying if I said I had any real basis for that guess