Note that in order to query the data type, you need to compile the model first. Try the following example:
vdp
% open the model
vdp([],[],[],'compile');
% compile the model
h = get_param('vdp/Mu','Porthandles');
% get the port handles
get_param(h.Outport,'CompiledPortDataType')
% get the output port data type
vdp([],[],[],'term')
% terminate the compilation
For a generic model name such as 'gcs', consider using the EVAL function. Here is an example:
vdp
eval([gcs,'([],[],[],''compile'');'])
h = get_param('vdp/Mu','Porthandles');
get_param(h.Outport,'CompiledPortDataType')
eval([gcs,'([],[],[],''term'')'])
