What the last two posters describe is a concept that is, apparently, known as Flügelzug ("winged train") rather than Kurswagen - according to the Wikipedia article mentioned earlier. A Flügelzug is a train that splits in half. A Kurswagen is a coach that gets hooked onto different trains in the course of its journey. Back in the good old D-Zug days you would often get trains with coaches to half a dozen different destinations, enabling passengers to travel half-way across Europe without ever leaving their seat.