The first thing that is needed is a python script.  The below is an example that we’re not using at the moment, but it merges multiple transit line files together.

import arcgisscripting, sys, os
gp=arcgisscripting.create()

gp.AddToolbox("C:/Program Files/ArcGIS/ArcToolBox/Toolboxes/Data Management Tools.tbx")

print sys.argv

input1=sys.argv[1]
input2=sys.argv[2]
output=sys.argv[3]

in1=input1+input1[input1.rfind("\\"):]+"_PTLine"
in2=input2+input2[input2.rfind("\\"):]+"_PTLine"

input=in1+';'+in2
input=input.replace("\\","/")
output=output.replace("\\","/")

print input
print output

if gp.Exists(output):
    gp.delete_management(output)

#input=input1+"_PTLine" +';'+input2 +"_PTLine"

gp.Merge_management(input,output)

print gp.GetMessage

del gp

To call this, we add the following in a Pilot script:

*merge.py {CATALOG_DIR}\Inputs\Transit.mdb\Routes1 {CATALOG_DIR}\Inputs\Transit.mdb\Routes2 {CATALOG_DIR}\Inputs\Transit.mdb\RoutesCombined

This makes it easy to create geoprocessing steps in ArcMap, export them to Python, and call them from the model.