I don't recall, honestly, and I don't have a copy of VB to test it out. Anyway, the only documentation I could find seems to indicate that that was not the intended behavior anyway.
As for C, no, it never behaved that way. C maps the case labels (which must be integer constants) in jump tables and obviously throws a fit if one of the labels is duplicated.
Just out of curiosity, I cannot figure out the advantage of using that particular artifact. Care to elaborate?