Private transit agencies don't provide good service because a private company is for-profit. This means that only the most reliable routes will remain open. As this is only one route, there isn't much choice. The line will either make money or not. However, for it to make money the prices have to be high, because the only funding is coming from the fare-box. In a public transit system/whatever, the price is set reasonably low, and reliable service can be provided because the agency is never at a shortage of money. Of course, Ontario transit systems are always short of cash, but that's a completely different story. I am generalizing here. The Heathrow Express and Connect are good counter-examples, granted, but imagine how much less it would cost, were it government owned.
I don't even know where the 99-year lease thing came from, but I certainly hope it doesn't happen. I mean, Blue 22 will only be using some of the tracks, some of the time, while GO and VIA have just as much service, if not more, and they need something to drive on too.
Forgive me, I am generally anti-PPP, because the taxpayers can really get screwed, and the workmanship can be shoddy. Let's take the Canada Line for example, everyone claims how it is a huge success of PPP, but the reality is, that the final price tag was so low because of some major points:
-The trains only have two cars, shorter platforms, less rolling stock needed
-Through downtown, the tunnels are one on top of the other.
-You only need one tunnel, for both trains, common throughout the world, but the two-tunnel Toronto system is much less cost-effective.
-Back to the rolling stock, there are hardly any seats, because it is an airport line, a minor concession, but it can add up
In the end, the Canada line isn't all that great, and it isn't even compatible with the rest of the Skytrain lines. VIVA went rather well, granted as well, but keep in mind that the fares and routes and design were all set by the YRT, so it isn't exactly a viable comparison.