This site give good information about Mode S operations.
EUROCONTROL - Mode S Operational Overview
http://www.caa.co.uk/docs/7/DAP_SSM_..._Factsheet.pdf
Both documents state that ATC can interrogate selected altitude and Aircraft call sign.
Enhanced Surveillance
Mode S Enhanced Surveillance provides all the functionality of Elementary Surveillance but, in addition, it provides Data Link functionality and access to further DAPs. In order to achieve this, the aircraft must have an interface between the transponder and its avionics system. The additional DAPs available are divided into the following 2 categories:
Aircraft Current State Vector Information
The aircraft current state vector information indicates the current state of motion of the aircraft. The information available includes:
(1) Ground Speed.
(2) Track Angle.
(3) Turn Rate.
(4) Roll Angle.
(5) Climb Rate.
(6) Magnetic Heading.
(7) Indicated Air Speed.
(8) Mach No.
Aircraft Intention Information
Aircraft intention information may be available from the avionics to indicate the future path of the aircraft. This information may be displayed to controllers and used to enhance Safety Net systems such as Short Term Conflict Alert (STCA). The information available includes Selected Altitude and the Barometric Pressure Setting on which this is based.