We were told the same thing on Tuesday when I went. That was a particularly eye-opening statement, and certainly one at odds with the many people that contemplated putting the Toronto station anywhere else. And when pressed about the stations at Ottawa, Montreal and Quebec, only at Montreal was it seen as being a requirement to locate the Alto station nearby Gare Centrale.
The other interesting thing was that there was a bit of contradictory information between stations at the event. For instance, at one station I asked rather pointedly about the potential need for wildlife crossings along the line, and was told that the line would not be a totally sealed corridor so wildlife could cross through without much issue (barring that a lot of species have a great hesitance to crossing wide open spaces). Another location specifically commented about having a fully-sealed corridor for everyone's safety, with the need for features to allow intruding wildlife the ability to escape. And yet a third commented that they were a requirement, and especially in light with the ancestral hunting and gathering grounds of the local First Nations people.
My other take-away from the event was that the people manning the event were not some sort of organization hired specifically for this kind of thing. Many of the people there spoke very knowledgeably about specific details that they were investigating for the line, without giving away too much detail about the way that they were leaning. These were people directly involved in coming to some of the conclusions reached to this point. It was quite refreshing to get proper answers - in as much as they could give - rather than waffle-speak.
Dan