The variety is 'Dwarf Empress', a genetic dwarf listed in various sources as hardy to zone 4 or 5. Another peach variety that is supposed to be hardy to zone 4 is 'Reliance'. So apparently it is possible to grow a peach tree in zone 4, which technically means that it should have a chance of doing okay in an urban or sheltered zone 3 location. In fact, I remember reading a story somewhere about a farmer in Grande Prairie who really (really, really) wanted to grow peaches, so he did. All he had to do was build a greenhouse over top of his peach trees. I suppose the moral of that story is that you really can grow anything you want to, if you're willing to put in the time and resources required.
So should I buy a peach tree? My guess is that the tree would most likely survive if it had good snow cover or if I mulched it, although I might need to prune out some winterkill most years. However, for many marginally hardy plants, the plant is more hardy than the flowerbuds, so it's quite likely that it often wouldn't bloom or produce peaches. The other risk is that even if the flowerbuds make it through the winter, an early blooming period would mean that the flowers would get nipped by a late frost, meaning no peaches. But some marginally hardy plants will bloom below the snow line, because those flowerbuds are protected by the snow cover. So if I bought a dwarf tree and piled a lot of snow over it, or lightly packed straw over it and wrapped it in burlap, I may indeed be able to grow peaches in Edmonton. Or I could just plant an orchard and build a greenhouse over it, and grow bananas and mangoes too.