Ok I'm not exactly sure what happened, but:
-Have you imported in the new scene the head with the sliders? Or have you just brought the head, with the sliders already there?
-Have you tried to import the "real" scene into the test scene? I know this is not convenient, but at least it could solve your problems.
-Have you tried to save your expressions and reload them in the new scene? You can do this by clicking on Save on the bottom of the Expression editor and then clicking on Select and choose the expression you wish.
-Another thing you could do is open a second Softimage, open the expression editor in both program, and rebuild all your expressions in the new scene, while switching to the other interface for reference.
-I suppose that you're using weighted shape interpretation. Is it a lot of troubles to simply re-write your expressions? I know that writing expressions for 30 shapes can be quite fastidious, but since the expressions themselves are pretty simple (mostly click-and-select), this is only a matter of time.
Hope this helps
Bernard Lebel