Unfortunately that is not possible.
PLCSIM works in the way that it "steals" the access point for MPI, and this only functions with Siemens own products such as STEP7, Protool and WinCC Flexible.
You can simply change your Citect SCADA Port Name (Communication / IO Devices) from say Port1 (or whatever you have called your Port)
to DISKDRV or MEMORY and you will be able to run Citect SCADA as
though it is talking to a PLC. Use DISKDRV if you want values to be retained or MEMORY if you don't want values to be retained from one running of Citect to another.
Of course you will have no PLC function simulation just simulation of the data transfer to and from the PLC. I find this very useful when setting up Citect SCADA if no PLC is available at the time.