Hi Anuj,
Yes. If I understand you correctly you want to use the WNS to provide a Toast for your app and not have the app create the toast correct?
You would create the infrastructure in a service to post the toast notification.
See this.
http://msdn.microsoft.com/en-us/library/windows/apps/hh465385.aspx#toast_notifications
http://msdn.microsoft.com/en-us/library/windows/apps/hh465452.aspx
-Jeff