When you open the client's project with Test Studio 2012.2.1527, Test Studio automatically changes  the namespace for example from Vontobel_Derinet_CH to Vontobel_Derinet_DE, so there is no complilation error.
In Test Studio 2013.1.911 you have to manually change the namespace or you will receive compilation errors. 

The test project is attached in the internal description.