Luxembourg state railways CFL runs some passenger services from Luxembourg into Germany, for example the RE11 Regionalexpress line Koblenz-Trier-Luxembourg. In addition to that CFL Cargo runs cargo trains almost everywhere in Germany.
The picture above shows a CFL's doubledecker Stadler Kiss type train on line RE11 at Trier main station on 18.12.2016. Picture by Ilkka Siissalo.

This picture shows a Luxembourg state railways CFL double decker Stadler KISS train (behind) coupled together with a German state railways DB train of type Stadler FLIRT. They run the RE11 regionalexpress line from Koblenz to Trier coupled together. In Trier the units are separated and the CFL train continues to Luxembourg. This is a quite unique combination. Picture from Trier station 18.12.2016 by Ilkka Siissalo.

Another picture of a CFL KISS kissing a DB FLIRT. Probably nowhere else in Europe regional trains of two national rail carriers run combined like this.
Picture from Trier station 18.12.2016 by Ilkka Siissalo.

A three coach KISS and a four coach FLIRT makes up a long train.
Picture from Trier station 18.12.2016 by Ilkka Siissalo.

A MaK G1206 diesel locomotive of CFL Cargo Austria, here at the works of neg, which by then was a subsidiary company of CFL.
Picture from Niebüll 9.7.2016 by Ilkka Siissalo.