Amazing what happens when the private sector is allowed to build stuff.
I'm trying to figure out how the private sector built the airport.
Sure, construction companies are private, but virtually all construction activity in Canada is done by private construction companies and trades. I assume this isn't what you mean or 401 was also privately built and a fine example of what we get when the private sector builds stuff.
GTAA is about as independent of government oversight as Toronto Hydro, the LCBO, or the Toronto Port Authority, etc. Crown corporations can do essentially anything they want, until they mess up really badly and it becomes political again (Ontario Hydro anyone?).
Do you mean the source of funding? Issuing bonds? If that's the case, then virtually everything the City of Toronto builds is also private to a certain extent. Almost all new construction and many large repairs in Toronto raise capital funds by selling bonds or taking loans. The only exceptions are when the province or feds kick in some money.
Payments to the bonds come out of the operational budget. So, when Toronto borrows $X in capital this year, we're really only borrowing about $X-$Y since we pay out $Y on existing loans from the operational budget. I think expected numbers are $X=500M and $Y=300M, but I'm not entirely sure.
For example, the new subway purchase is about 30% privately funded; TTCs portion if the Feds come through. It will be closer to ~60% privately funded if the feds don't contribute towards them.