Well if you're so certain, let's talk numbers. How many people do you expect to be using the line per hour at the peak point at the peak hour? Where will the peak point be and why? What's your breakdown for where the new riders will be getting on? Where are the new riders coming from – i.e. how many will be coming say from STC, how many will be new users from existing developments, how many will be new to transit but that currently live in the area and how many will be from new developments? How did you come up with those numbers? On a related note, what mode share do you expect transit to get with all these new condos? What leads you to that particular conclusion?
So far you've still been speaking about your gut feelings. You can't pull numbers out of the air like that. Well, I guess you can.. but you shouldn't. Because if we're playing that game I'm going to insist that we install a subway to North Bay – my gut feeling is that it'll be super profitable.
The TTC/Metrolinx came up with their numbers by doing an analysis based on all sort of statistical data. Yes, there are a lot of assumptions built in, but that's how you challenge their numbers – by challenging their individual assumptions. Picking a new number of out the air and accusing the TTC's numbers of being unrealistic (or as you put it - "the inaccurate ridership projections that the Miller administration created") just reenforces that you're not to be taken seriously because you don't know what you're talking about
TL;DR - If you want to challenge ridership projections, bring your own data to the table and explain how you came up with those numbers