Finally I've found the way to retrieve it!!!
Statusing.ReadStatusTimephasedData
Edit:
This method return the statusing data for the currently logged user. If the user is the project owner, it will get the data for every assigned resource. Otherwise, only the user's data will be returned.
In order to retrieve the whole of the data (every project and every resource), the [PSI impersonation][2]
must be used.
But that is not possible in my case, so I am developing a [PSI extension][3]
to expose the information I need and [custom permission][4]
to control access to it.
[2]: http://msdn.microsoft.com/en-us/library/aa974347(office.12).aspx
[3]: http://msdn.microsoft.com/en-us/library/bb428837(office.12).aspx
[4]: http://msdn.microsoft.com/en-us/library/aa974255(v=office.12).aspx
NB: I cannot post more than one link yet :P