CC
I challenge your idea to extend the Eglinton line to Eglinton and Hurontario.
1) Your straight cross-border extension would make it very difficult to build an airport hub at Pearson as envisioned by Metrolinx and the TTC.
2) There is no significant development between Hwy 427 and Hurontario along Eglinton that can't be serviced by regular buses.
That being said Transit City does propose building a Mississauga spur to the Eglinton line. Perhaps citizens in your city should start pitching councillors to come up with the cash to extend the Eglinton LRT down Eglinton towards Square One. At around 13 km in all, and likely to require some tunneling or bridging it's going to be pricey though.
An alternate route is running LRT along Burnamthorpe from Hurontario till Islington Station, about 12 km, though this would require relocating the best terminal to the south side of Square One. I wonder if there is development along Burnamthorpe to justify the price tag, though it might be justifiable from a network point of view. I also wonder how this would operate, having a TTC surface route operating in 'sauga or conversely if MT was operating this, then what about the portion that would operate in Toronto?
All in all, I think it'll be quite challenging to work with Mississauga on a TTC subway or LRT. First there is the cost of construction. Next there is the issue of revenue and service outside of jurisdiction, etc. For this to happen, Mississauga would really have to step up with hundreds of millions (maybe a billion) dollars and be willing to swallow their pride and let the TTC run the show. I am skeptical that Mississaugans would even support such an extension if that meant a significant increase in taxes...which would be likely.
It's quite a different case up north, Vaughan practically fashioned a new city centre around the subway stop. And it's also willing to step up with cash, let the TTC take all the revenue, and let the TTC dictate the rules. That's co-operation.
For now, the Metrolinx proposal is best....let Mississauga build its own BRT/LRT down Hurontario connecting with Port Credit GO station Cooksville Go and let riders come in to Toronto on the GO lines. Most riders from Mississauga are due towards downtown Toronto anyway; few have any requirements to get off along the BD line. So this idea makes sense. Those who need the BD line can use existing buses to connect to the line or perhaps a cheaper BRT can be built from Square One to the BD line.