iPlanet has a tool: csexport.
The file extension of the OUTPUT file (.ics or .xml) determines the format it will export to: ither iCalendar or XML
So since suPump.exe takes an XML file as input for incorporation into Exchange, this gives a quick way of server-side migration.
You use it as follows:
csexport -c jsmithcal calendar jsmith.xml
suPump.exe /k /AT:UserID /u:jsmith /DT:A /file:"jsmith.xml"