I think GO purchased the Stouffville-Uxbridge segment to protect it from abandonment. It will take a fair number of years before any GO train service will go that far, in the meantime, the York-Durham railway has a 50s diesel trainset making public excurisons. I don't think putting up the Talents all the way to Uxbridge would make sense, perhaps Mount Joy is the logical terminus right now, though the extra transfer will be a pain.
The Bradford-Barrie segment of track was purchased by the province through Ontario Northland Railways to protect it as CN was going to rip up the entire track between Bradford and Washago, that was over 10 years ago.