Hi Kaustubh,
the XML-interface (neither the MS-Project) does not support the preparing of Auditplans with subordinate audit plans or audits.
Below SAP note explains the use of the XML for question lists:
597982 - Audit management: Initial load, offline scenarios, interfaces.
It can be useful, when you work with XML.
I hope I could help with this information.
Have a nice day,
Albert