I appreciate that you're trying to come up with a solution to the issue of investors snapping up low-quality housing that then sit vacant. I understand that this is a big issue in Vancouver condos and neighbourhoods. The foreigner tax on Vancouver-area properties goes a large way towards disincentivizing such investment.
That said, this article is about single-family housing in the GTA, where vacant lots are a much smaller issue. Demand here is driven by a large number of families who want to live in a particular style of home, they're paying up not just to park their money there but to have lots of space for their kids, cars, woodworking workshops, etc.
Even if these houses weren't occupied by owners, the families would still pay up to live there. Instead of high property values driving up the rents, you'd get high rents driving up the property values. Where there's demand, it doesn't matter much who invests. Investor money would always find them, foreign or Canadian.