So this is a script I wrote in order to automate putting objects into passes’ background partitions for either the active pass or multiple selected passes.  It is filed here

# Move selected objects to background partitions
 
# created by Gareth Bell
 
# original created in VBScript 28-11-11
# converted to Python 26-07-2012
 
 
# Description:
# This script will put the selected objects into either the current passes bg partitions or, if selected, multiple passes bg partitions
 
##################################
 
# To use:  select objects and passes. Run.
 
##################################
 
import win32com
xsi = Application
 
#create collections to store objects
geoColl = win32com.client.Dispatch( "XSI.Collection" )
passesColl = win32com.client.Dispatch( "XSI.Collection" )
lightsColl = win32com.client.Dispatch( "XSI.Collection" )
 
selection = win32com.client.Dispatch( "XSI.Collection" )
selection.AddItems (xsi.Selection)
 
#sort selection into collections (objects, lights and passes)
for obj in selection:
          if obj.type == "light":
                   lightsColl.AddItems (obj)
          elif obj.type == "Pass":
                   passesColl.AddItems (obj)
          else:
                   geoColl.AddItems (obj)
                  
passCount = passesColl.Count
 
#decide if sorting is in only the current pass or multiple passes
if passCount > 0:
          for eachPass in passesColl:     
			print str(geoColl) + " has/have been put into the background partition in " + str(eachPass.name)
			xsi.MoveToPartition(str(eachPass) + ".background_objects_partition", geoColl, eachPass)
			print str(lightsColl) + " has/have been put into the background partition in " + str(eachPass.name)
			xsi.MoveToPartition(str(eachPass) + ".background_lights_partition", lightsColl, eachPass)
else:
	currentPass = xsi.ActiveProject.ActiveScene.ActivePass
	print str(geoColl) + " has/have been put into the background partition in the current pass"
	xsi.MoveToPartition(str(currentPass) + ".background_objects_partition", geoColl, currentPass)               
	print str(lightsColl) + " has/have been put into the background partition in the current pass"
	xsi.MoveToPartition(str(currentPass) + ".background_lights_partition", lightsColl, currentPass)