By default, VisBuildCmd captures and displays console output of any child (grandchild, etc.) processes that the build starts.
When using the VBP object model, no output is automatically captured (there is no console to speak/capture output from/echo to when invoked in this way). Events are fired for the steps built in the parent .bld file, which can be logged and apparently is what you're referring to? There is no provision for automatic capture/echoing of child project output.
One option would be to launch VisBuildCmd from your launcher rather than using the object model:
http://www.visualbuild.com/Manual/visbuildprosample.htm
http://www.visualbuild.com/Manual/objectmodelsample.htm
Another would be to use XML logging (having all projects log to the same file) and generate/display an HTML log at the end of the build, which would contain output from all levels of child projects.
http://www.visualbuild.com/Manual/loggingsample.htm
http://www.visualbuild.com/Manual/tr...mlogaction.htm