Long story short: We're trying to set up Durandal SPA in our pre-existing ASP.NET MVC website. What's we're going for is the ability to hide the SPA behind a feature flag, to where we can enable the SPA flag and have our website adjust accordingly.
We have that portion of it working. However, what we had to do is prefix all of our routes with "/app#" and then tack on the controller/action. For example, "Index" would become "app#Index" in the URL. Durandal routing works just fine with this approach - it pulls the necessary views into place.
What we would like is to use the same routes instead of prefixing each one with "app#" - essentially use Durandal routing when the SPA flag is enabled, otherwise use normal MVC routing, but keep the routes the same.