I mentioned already that the Public Sector Accounting Board has a consultation paper out on this question. It is reflecting the discussions that are very current including those in the public accounts committee about what is the right way to think of these things.
Broadly speaking, there are two camps. There is the camp which says that it's legitimate to use some kind of assumed rate of accumulation on assets, and if your plan were fully funded I would certainly listen respectfully to that argument. When your plan is unfunded, though, there's no asset to earn the return, or for most of it. In a situation like that it's appropriate to leave the assets aside. They're not relevant. What you're focusing on is the value of the obligation, the value of the liability. That's where I think the compelling logic is to use the federal government's real return bond rate, reflecting the fact that this is an obligation. You said that the federal government isn't likely to go bankrupt. The bond deals reflect that. The pension discount rate should also reflect that.