It's also important to note that SF is already a destination for homeless people from other cities in the US. In some cases that's by choice; in others it's because the local authorities send them there simply to get rid of them (several noteworthy stories have come up just within the past few years). So it's quite likely that such a system would serve primarily to foist the cost of homelessness in other cities onto the citizens of SF, where, ironically, it's most expensive to address. If I were a citizen of SF, this would be my primary objection to such a plan. It's not clear how to prevent this kind of abuse in a fair manner.

This aspect was not mentioned in the article. Perhaps Medicine Hat is viewed as a less desirable place to live than, say, Vancouver, and therefore this hasn't been an issue. It's also possible that the Canadian legal system is more effective at preventing this kind of inter-provincial abuse.