To my way of thinking, a GO train (as in commuter-focused service) never made sense to Collingwood.
What did and to me still does make sense, providing travel times could be reasonable, for the scale of investment is tourist-class train travel.
Its a way for GTA-area folks to get up to Blue Mountain for Skiing or Wasaga for a swim.
In saying that, I realize the infrastructure cost would be an extreme challenge, particularly if it was primarily justified for a limited tourism service only.
The mix of investments required for upgrade and new spurs would be in the many millions, likely hundreds of millions, and that's a steep ask for light traffic.
Still, I had thought that if the track were also able to serve freight; and perhaps have a limited local service that connected the hinterlands to Barrie there might be a case to be made.
If there is such a case to be made, however, it will be at the margins and rank well below many other more crucial investments, which should come first.