Surely their comment was not explicitly stating that they needed to triple-track all the way to Kitchener? Mount Pleasant, for sure, but I can't imagine that they need it tripled beyond Georgetown, when they own the line, and dictate the schedules.
If you are going to do it right, then there needs to be 4 tracks where possible from Georgetown to Bramalea. I call for 4 tracks in the early 2000's when the EA was being done to add a 2nd track to the single track line. It was approved as a twin track, but became 3 tracks during the construction stage.
If this line going to be High Speed to London, Georgetown to Kitchener needs to be 3 tracks.
As it stands today, Georgetown to Mount Pleasant is 2 tracks and 3 from the station going east to just before the Orangeville crossing. Not sure if you can get a 4th track in at the Mount Pleasant Station and need to revisited it, but it look like only 3 when it was being built. A few overpasses will have to be rebuilt to get 4 tracks in.
It is 2 tracks from the Orangeville crossing to the east side of Queen St and can be expanded to 3. From the east side of Queen St to Bramalea, it is 3 tracks and can be expanded to 4 tracks.
You need to build a Fly-under at Bramalea to get from the Weston Sub to the north side if Metrolinx wants to keep it lines separated from CN. Down side are the platforms at Brampton and Mount Pleasant since they are on both side. You could run trains on the outside of the 3/4 tracks and leave the centre 1/2 tracks for CN.
At Georgetown, you need to build 2 more bridges over the Port Credit River and I believe they built the extra wide pier support for 1/2 new tracks when they built the 2nd track on the north side a few years ago. If you want to keep the 2 new tracks as well maintaining the current stations, then the outside tracks will be for VIA and GO and will require a Fly-under for the #4 south track to connect to the Guelph Sub so there is no interference with CN west of the station.
It is also time to look at building a new station and layover for Georgetown that been talked about for years.