I'm not sure that the numbers should be measured by civic boundaries or municipal rhetoric. Assess the density around Port Credit versus Oakville, consider the last-mile transportation alternatives for each location. Each location has a catchment, and the catchment is not defined by those municipal boundaries.
There's no reason to assume that the Hurontario LRT line will be a step change in the last-mile option for VIA travellers throughout that 828K city. It will for some, especially considering density along Hurontario and south of Dundas generally.....but Highway 403 still gets you to the Oakville station from much of Mississauga also.
I'm not saying that I disagree with Port Credit for VIA, but I'm saying your data point is not that compelling.
- Paul