How can I override a .svc file in my routing table?

The problem you’re running into is due to a build provider that is registered for .svc files. This build provider is registered by the default machine level web.config file.

In order to get routing to work in this case, you’ll need to remove the build provider in your application’s web.config file. The following snippet shows how to remove the .svc extension from the list of build providers.

  <system.web>
    <compilation debug="true" targetFramework="4.0">
        <buildProviders>
            <remove extension=".svc"/>            
        </buildProviders>
    ...