Don't know how this fits your usecase but I would emit a signal in the method that receives the dbus signal, connect it to the declarativeView and change the loaded qml file, or connect it directly to a qml signal to change the UI dynamically when the user clicks on the notification.

EDIT: The way I described does not require a service running to catch dbus signals. The OS searches in the dbus-1 folder and launches your application if it's not already running.

fo example if you put a .service file there that registers the service to com.qwazix.demo and has an exec=maps, if you do qdbus com.qwazix.demo / methodname 5 then maps will open, and methodname(5) will be called in the dbus adapter class (if methodname exists of course)