So now that HTML5 introduces history.pushState to change the browsers history, websites start using this in combination with Ajax instead of changing the fragment identifier of the URL.

Sadly that means that those calls cannot be detect anymore by onhashchange.

My question is: Is there a reliable way (hack? ;)) to detect when a website uses history.pushState? The specification does not state anything about events that are raised (at least I couldn't find anything).
I tried to create a facade and replaced window.history with my own JavaScript object, but it didn't have any effect at all.

Further explanation: I'm developing a Firefox add-on that needs to detect these changes and act accordingly.
I know there was a similar question a few days ago that asked whether listening to some DOM events would be efficient but I would rather not rely on that because these events can be generated for a lot of different reasons.

Update:

Here is a jsfiddle (use Firefox 4 or Chrome 8) that shows that onpopstate is not triggered when pushState is called (or am I doing something wrong? Feel free to improve it!).

Update 2:

Another (side) problem is that window.location is not updated when using pushState (but I read about this already here on SO I think).