Alas not, the whole installation of CSSU is meant to start from a clean maemo stock, there are no methods to uninstall or switch branches (e.g. camera-ui would need uninstall when switching from T to S) - so it can not work without clean reflash to stock and installing from there. However, I hardly can see a lot of users wanting to move from T to S (and actually it *might* be possible to migrate from S to T as T is supposed to be "just newer" than S)