As of this moment, the answer is NO
Derick Bailey opened this issue on Backbone's repo suggesting some changes to backbone's structure to support such a change: https://github.com/jashkenas/backbone/pull/1630
There followed a discussion of the merits of such a change, where the following point was made:
To get started -- I'm afraid that I don't understand the premise here. There are a couple axioms of routing that contradict this patch:
Routers exist to match URLs to locations in your application.
The whole point of URLs is that they're always reachable -- once you have a URL, you can go back to it (bookmark it, paste it into a browser) at any point.
I also went over the Backbone source code, and there is no indication that the functionality I am thinking about is possible.