Solved! So, we need to add a route contraint to the webforms route to ensure that it only catches on incoming routes, not outgoing route generation.
Add the following class to your project (either in a new file or the bottom of global.asax.cs):
public class MyCustomConstraint : IRouteConstraint{
public bool Match(HttpContextBase httpContext, Route route, string parameterName, RouteValueDictionary values, RouteDirection routeDirection){
return routeDirection == RouteDirection.IncomingRequest;
}
}
Then change the Tickets route to the following:
routes.MapPageRoute(
"Tickets",
"Reports/Tickets",
"~/WebForms/Reports/Tickets.aspx",
true, null,
new RouteValueDictionary { { "outgoing", new MyCustomConstraint() } }
);