1st stage phone interview:
general c++ questions from all possible areas: constness, inheritance, smart pointers, templates, STL, multithreading etc.
Example: What is 'mutable'? Give an example where you used it.
2nd stage inhouse interview:
Four tasks - I had to write code on paper. The last one was to write tree-related algorithm.
Overall it wasn't difficult, but I failed because I did a few stupid mistakes in a basic questions. So my recommendation would be: review basic concepts and not only advanced.