Not sure if it helps any, but the administrator's email address is listed in the wt.properties file. Maybe you can either retrieve the property with Java or manually parse the file. (It's available anonymously from <windchill url>/Windchill/wt.properties)
Look for these properties:
wt.mail.from=
wt.org.principalAdministratorEmail=
wt.notify.notificationSenderEmail=