I would assume that the arena would be almost entirely privately funded. The city is already in hot water for RIM park (which is a maginificent sports complex containing Gyms, Arenas, Soccer field, Baseball diamonds, etc.). And while he would obviously bring RIM with him, getting some of the insurance companies (Sun Life, for example), and Toyota on board would be crucial. The trick is that IF he can't get an arena for free in Pittsburgh and he is shelling out the cash anyways, then so be it.
I think the luck is having a billionaire running a company in Waterloo buying the team. The arena would be a HUGE issue, and is one that would almost have to be done out of pocket. Ottawa's arena was basically a mirracle that couldn't happen again. And your right, once Melnyk got the arena and team for half the price of the arena, Ottawa's finances changed from flaky to extremely strong.
If Pittsburgh doesn't get the arena, there are other markets that will be willing to offer arena subsidization. The U.S. has a greater culture of subsidizing sports franchises. The issue of getting an arena for free can really tip the scales in favour of a town that may not possess as much revenue potential.
What can tip the favour towards a southern Ontario location, is if by building a privately funded arena, there is usually much more control, and, if the owner purchases the surrounding area, they can make a lot of money on the development. I really hate to see that type of business model, as, it usually creates an unstable mess. It makes the hockey operations secondary, and can lead to bad team management. One has to look at what Charles Wang to find evidence of that.
I also don't know if the RIM owner wants to get into major land development deals. It's not his area of business, and, he may not want to be getting involved in that. Perhaps he takes on a minority partner for the arena for this purpose. I also know that the municipal government is currently trying to bring a 5-star hotel to the area, so the idea of a development park with an arena fits into those plans.
If the owner wants this to happen, in the event that Pittsburgh doesn't get the arena, there is enough potential out of this idea, that if the owner is very keen on it, to the point where he'd forego a partially funded arena in another city, like Kansas City, there are enough factors that he could probably push this through, and make it work.
Regarding someone else's comment about Mississauga not being a business centre, I highly disagree. I've dealt with a number of business in the Mississauga area. There are plenty in the surrounding offices, and, many of these are smaller offices of major international companies. Their presence in Toronto is as a sales office for Canada, which is why they are near the airport. These are the type of organizations that use hockey tickets in their business operations. Many are likely Leafs ticket holders right now, but, a KW team gives them a lower priced option, or, just a more readily available option, with the Leafs having such high demand for their tickets.
The distance remains an issue, as, that 401 corridor to Cambridge is a heavy traffic route, but, it isn't unmanageable. I've been on that route during high traffic times, and, I think the Orleans to Kanata comparison is apt.