I don't believe there is a huge concern about contracting out services - just selling the airport to a for-profit entity. In a competitive market private companies take steps to satisfy customers because they have buying options. In a near monopoly that incentive to customer service is gone and you need to have regulations and oversight to ensure customers are not taken advantage of (e.g. CRTC, various provincial energy boards, etc.).

However, we have seen time and again that governments are not good at devising these agreements and managing them (e.g. Ontario's 407 disaster).

Why take a risk that is irreversible? There is no compelling need to privatize airports. We have no expectation airports will run better or cheaper.