Yes (I think).
First filter for files that have CD in the filename
%_path% MATCHES CD\d+
and import the data with a mask like
%artist%\%year% - %album%\CD%discnumber% - %discsubtitle%\%dummy%
then filter for files that do not have CD in the filename
NOT %_path% MATCHES CD\d+
and import the data with a mask like
%artist%\%year% - %album%\%discsubtitle%\%dummy%
You cannot have 1 mask for 2 different patterns.