CC can only open CC characters which are iAvators of a specific generation (post-G6 basically).
However, you can use the clothing by exporting them as an OBJ file, which you can then import into CC.
I have to do some research as to the steps, but I have do this with even older clothing and it worked. There is indeed a treasure trove of older clothing that can now be tapped.
EDIT: It's bit more involved than I thought, but it IS possible because I've done it.
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