There are references in Die Vertreibung der deutschen Bevlkerung aus den Gebieten stlich der OderNeie to the relocation to the former German territories of residents of destroyed Warsaw and  the employment of German forced labor in the clearing operations in post war Warsaw   Also the Polish census data from  indicates that  former residents of pre war Warsaw city and Warsaw province were resident in the Recovered Territories in Dec    The refugees of destroyed Warsaw needed a place to stay and somebody had to clean up the mess and rebuild the city   One cannot now deny that the Expulsions and the destruction of Warsaw are related