constructor(@Inject(AuthenticationService) private authSvc: AuthenticationService){
        this.authSvc.getAuthChangeObservable().subscribe(data => this.onAuthenticationChanged(data) );
  }

private authChange: Observable<any>;
private _authObserver: Observer<any>;

constructor(@Inject(FirebaseService) firebaseService: FirebaseService){

    // Cookies or whatever allow .auth() to identify the user after a page refresh
    // This causes a slight delay, see my question below
    firebase.auth().onAuthStateChanged(user => {
      if(user) this.onAuthenticationSuccessfull(user);
      else this.onLogoutSuccessfull();
    });

    // Create an observable for auth status
    this.authChange = new Observable(observer => {
      this._authObserver = observer;
    }).share();
  }

  getAuthChangeObservable(){
    return this.authChange;
  }

...

onAuthenticationSuccessfull(user){
    this.authenticatedUser = user;

    // This is mainly the way I found to warn other services they are clear to load the
    // user-related data
    this._authObserver.next('auth');
}
...