The old pathway ran on the other side of the tunnel (on the inside of the curve, where the east-bound tracks now run). That way the sidewalk could easily go from Tremblay Road, through the tunnel, to the east-bound Transitway bus platform.
I'm not sure how the same, simple, pedestrian connections can be made with the current configuration within the tunnel:
Assuming that a path will be added (although the current grading doesn't look to me as if it supports that theory), it would likely be added on the outside of the curve, outside the (new?) pillars. Such a path would connect a fare gate to the west-bound platform to where? It would emerge from the tunnel between the tracks and the 417.
The old pathway was convenient for people to easily get to the Transitway station. When that path was removed, during the construction for the LRT, there were complaints. The City's response was to say that they would endeavour to make sure that the path would be replaced. I don't see that happening within this tunnel. I think that we can chalk this one up to another loss in the 'Ease of Access' column.
There used to be a paved pathway, near the 417 structure, from the sidewalk along the east side of St. Laurent up to a death-defying crossing of the 417 on-ramp and bus ramp, but that path got messed up during the widening of the 417 structure and has not been rebuilt. I have used that path a few times, but it is decidedly un-friendly. Also, the sidewalk over the bridge from Labelle Street isn't too bad until you get to the shopping centre end; at which time the 'sidewalk' disappears and pedestrians are abandoned to their own courage. The St. Laurent OLRT Station looks as if it will be solely for the use of OC Transpo customers transferring from/to buses and patrons of the shopping mall.
On an unrelated note: Notice that the 'catenary' in the tunnel is a suspended 'rod', and not wire.