Hi Tamer,
Looks like there is no support interfacing MATLAB/Simulink with 'PSCAD' for now. Maybe you can reach out to the 'PSCAD' technical support for any other help on the interfacing 'PSCAD' with Simulink.
Also, the Co-Sim functionality in 'PSCAD' is bunch of C functions, maybe it can help if you look at the MEX functions in Simulink which allows for the implementation of 'C' code in Simulink.
I hope this helps!