>>> arcpy.ImportToolbox(".tbx")
# Run the imported tool
#
>>> arcpy.toolname_alias(parameters)
When accessing tools using the arcpy package, the toolbox alias is extremely important. If a unique name is not used, then the system will not know what tool to run.
When working with server, published geoprocessing tasks can be imported as well:
>>> arcpy.ImportToolbox("http://server/arcgis/services;BufferByVal")
Enjoy