Actually, I think FATCA is evolving toward an intergovernmental system, because FATCA, as drafted, really doesn't work very well. It's just incredibly intrusive.
The United States has developed several models of intergovernmental arrangements, and it's negotiating currently with more than 50 countries. I think it's probably already negotiated with Canada. I haven't followed it on a day-to-day basis.
This is not contemplated by the legislation. The Internal Revenue Service, commendably, has converted FATCA into more of an intergovernmental arrangement.
As to whether it would work on a multilateral basis, I have some real doubts. It's very expensive for financial institutions to comply with. And if you had to comply with similar legislation throughout the world, with all countries asking banks, I think it would be quite a burden.
On the other hand, you could argue that it's one of the reasons why FATCA is a poor piece of legislation. If you pass a piece of legislation that you don't want to have coming in your direction, that's a suggestion that the legislation had some defects to begin with.