I was surprised and confused by Winnipeg's back lanes as well. I'd never encountered that before. Since returning home, I've scoured St. John's for comparable lanes but I've only found one:
We have lots of narrow lanes and back lanes and alleys and all of that - but this is the only lane I could find that is comparable to those of prairie cities in that its only purpose is to provide secondary access to residential properties and a place to put out the garbage.
All the others have separate homes, businesses, etc. that can't be accessed from the main streets surrounding. So they don't really count as back lanes in the same way to me:
I still can't believe cities that have these are paying for two paved streets for every single-family, detached home. Insane.