Here's a schematic diagram of the track arrangement shown in the Metrolinx submission. For context, I have also included the planned track configurations east and west of the USRC, as well as the 11-track pinch point at John Street.
View attachment 457974
To get a rough idea of what the typical use of each platform might be, I did a simple connect-the-dots exercise to fill in the unknown sections. Please note that I gave very little thought to these conceptual layouts, they are really just intended to give a ballpark idea of where tracks end up.
Here's a version with the existing flyunder.
View attachment 457984
Track 1: Barrie
Track 2: Barrie / Richmond Hill
Track 3: Stouffville/Kitchener Local westbound
Track 4: UP Express
Track 5: Stouffville/Kitchener Local eastbound
Track 6: Milton
Track 7: Kitchener Express / VIA Sarnia
Track 8: Kitchener Express
Track 9: Lakeshore Local westbound
Track 10: Lakeshore East/West Express
Track 11: VIA Ottawa/Montréal
Track 12: Lakeshore West Express
Track 13: VIA Windsor/Ottawa/Montréal
Track 14: Lakeshore Local eastbound
Here's a version where the flyunder is removed:
View attachment 457975
Track 1: Barrie
Track 2: Barrie / Richmond Hill
Track 3: Kitchener Express
Track 4: UP Express
Track 5: Kitchener Express / VIA Sarnia
Track 6: Stouffville/Kitchener Local westbound
Track 7: Stouffville/Kitchener Local eastbound
Track 8: Milton
Track 9: Lakeshore Local westbound
Track 10: Lakeshore East/West Express
Track 11: VIA Ottawa/Montréal
Track 12: Lakeshore West Express
Track 13: VIA Windsor/Ottawa/Montréal
Track 14: Lakeshore Local eastbound
I'm pretty sure that track 4 is for the UP Express given how small it is, and this version places it on the north pair of tracks in the Kitchener corridor, which doesn't make sense since it splits off toward the south at Wice (Pearson Junction). Based on that, my guess is that they are planning to keep the flyunder in the USRC.