The pricetag. Not to mention the Peterborough route is never likely to be as fast as the existing route. Look at how slow trains were on that line from Toronto to Ottawa when it was still used. Look how curvy it is - you'd pretty much have to build miles of new alignment. You aren't accomplishing that for only $4 billion.
I'm going to respectfully disagree with you on a few points here. I don't think the Peterborough routing is out just yet, based on the info we have.
Here is a map of the a potential Peterborough route:
VIA has budgeted $2 billion for "
infrastructure", which is assumed to be track infrastructure. The existing route requires track to be built
alongside the existing track, whereas the Peterborough route requires track to be upgraded, and relaid on an existing, but abandoned right of way. I'd only assume the latter is cheaper. In terms of speed, the Peterborough route is actually shorter due to trains not having to make the run from the lake to Ottawa -the Peterborough route gradually arrives in Smiths Falls and then runs to Ottawa, reducing the overall distance. Also, besides a curve near Marmora the route isn't actually that curvy, at least not bad enough to really impact the speed of the trains.
I again agree it would be better to put it by the lake, but I'm not ready to rule the Peterborough routing out just yet. Especially after the Metrolinx RER report that was talked about a few days ago explicitly said they weren't sure if VIA HFR was via the lake or via Peterborough. Again, I don't pretend to know everything so correct me if I misinterpreted anything.
Also just a general question, will HFR require the entire VIA route to be double tracked, or will long sidings due just fine?