This is a bad example imo. These were useless freight lines for the longest time, and set to be abandoned until GO took them over in the 80s. Those houses existed long before then. Expropriation and even buying them up is not an easy process. Once this line is electrified with 5-15 minute service all day, you will see a change in the areas along the line, as the value of the property will become so lucrative only an idiot with a spite house agenda would keep their property.
This isn't a housing failure its a transit failure. GO sat on these single track lines for 40+ years and did barely anything to improve them when they owned them and had no competitors or freight to contend with. The work that's being done now should have been done decades ago.