moced source files are output to the same directory, prone to filename clashes

A simple example of a source file directory structure:

client/MyWidget.cpp
server/MyWidget.cpp

Normally, VS2010 outputs all object files to the same intermediate directory $(IntDir) like so:

obj/MyWidget.obj
obj/MyWidget.obj

Obviously this is a problem since the first object file is overwritten by the second. The standard way to resolve this is to change "Object File Name" in "Configuration Properties -> C/C++ -> Output Files" from the default "$(IntDir)" to "$(IntDir)/%(RelativeDir)/", which gives this:

obj/client/MyWidget.obj
obj/server/MyWidget.obj

Problem solved. Unfortunatly, the Qt Addin suffers from similar problems. moced source files are output to the same directory. Changing MocDirectory to ".\GeneratedFiles\$(ConfigurationName)%(RelativeDir)" doesn't resolve the problem. mocced source files are output with their directory structure intact, i.e. "GeneratedFiles/client/moc_MyWidget.cpp", but the second MyWidget.cpp file is not mocced, and "%(RelativeDir)" isn't expanded by ClCompile.