Since Simulink works file-based you can use SubVersion also without the SCCI interface.
Models and other necessary files can be provided for version control by simply checking in the appropriate files. For SubVersion there is a common free tool TortoiseSVN
To ensure that all necessary files are checked in for version control you could use the Simulink Model Dependency Analysis:
To see if an already opened model is chosen see the Model File Change Notification in Simulink:
