Based on that link, it appears that one workaround may be to use devenv rather than vcbuild (select devenv in the Override field on the Options tab of the Make VS.NET action).
Yes, VBP will inherit the PATH of the process that started it, so another option would be to start VBP from a Visual Studio Command Prompt.
Or, you can alter the PATH environment during the build by using a Set Macro action to create a temporary PATH macro, with 'Add to environment variables' checked and a Value like %PATH%;c:\extra\path1;c:\extra\path2...
http://www.visualbuild.com/Manual/setmacroaction.htm
http://www.visualbuild.com/Manual/advancedsample.htm