My first question is "Where are they keeping all these people?" Previous attempts to just build enough housing for everyone[1] haven't turned out all that well, and they became cesspools of crime.
Beyond that, are the conditions in Medicine Hat such that they can be replicated everywhere? Perhaps Medicine Hat just has an abundance of housing.
And lastly, it doesn't seem clear to me that they actually have eliminated homelessness. Other news sources claim that they will eliminate homelessness "soon"[2] or that they have "almost" eliminated homelessness[3].
[1] http://en.wikipedia.org/wiki/Pruitt%E2%80%93Igoe [2] http://www.huffingtonpost.ca/2015/05/14/medicine-hat-homeles... [3] http://news.nationalpost.com/news/canada/medicine-hat-has-al...