let times = true;

// This is a mock method for your http.get call

const httpMock = () => {

  if(times) {

    times = false;

    return Rx.Observable.of({items: ["1", "2", "3"], next: true});

  } else {

    return Rx.Observable.of({items: ["4", "5", "6"], next: false});

  }

}

​

httpMock()

  .expand(obj => {

    // In your case, the obj will be the response

    // implement your logic here if the 206 http header is found

    if(obj.next) {

      // If you have next values, just call the http.get method again

      // In my example it's the httpMock

      return httpMock();

    } else {

      return Rx.Observable.empty();

    }

  })

  .map(obj => obj.items) 

  .concatAll()

  .combineAll()

  .subscribe((val) => console.log(val));