I've played a bit with the WebEx XML API and everything works fine so far (simple get/set-requests).
Now I’d like to find out, which user uses a particular “mpProfileNumber”. The reason for this is, that we use WebEx in combination with MeetingPlace. Sometimes our users report login issues and that is caused by a “mpProfileNumber” which used by another account. (MeetingPlace uses the last 8 digits of the phone number as the Profilenumber. When the user logins into WebEx the authorization is handled by MeetingPlace and MeetingPlace passes the user details - including the Profilenumber and the user id - to WebEx.
The mentioned issues occur, if there is a new employee who gets a phone number which was used by someone else or if an employee changes the last name --> new user id. In both cases there is now a user account, which uses the same Profilenumber in MeetingPlace as the old user account has been using. During the login process WebEx gets the new user details, but denies the login because of the “mpProfileNumber”, which is used by the old WebEx account.)
As the WebEx user export file does not contain the field “mpProfileNumber”, it’s a bit difficult to find the user account which causes the issues. So my idea was to use the WebEx XML API. But the response of “lstsummaryUser” does not contain the “mpProfileNumber” and the “LstUser” request is deprecated.
I'd be really happy if someone would have a solution for this... 
