The user is then prompted to select a curve object (this may be a Line, Polyline, Arc, Circle, Ellipse, XLine, Spline etc.) to which the selection of objects are to be aligned. The selected curve may be a primary object, or an object nested with a Block or XRef, nested to any level.
Lee writes that it also works on X-Ref and that goes also.
Ok snap does not go sorry must read more.
Lee schreibt das es auch auf X-Ref funktioniert und das geht auch.