I had seen this train at the blog Opvallend onopvallend of fellow blogger Marleen but hadn't seen it myself yet. The orange "Kings" train went through the Netherlands in honor to the inauguration of King Willem Alexander on. April 30 and to stimulate people to use a train ride. Apparently it is still riding around as I saw it this week in Amsterdam!
It has a text at the side "Go with us from Beatrix to Alexander" which is not so up-to-date anymore.