It would be like Nortel when it was trading on  both the TSX and NYSE.....dual listing.  The company said in the PR that the TSX lisitng would be maintained.

Picture it like a warehouse, in the warhouse on the shelves are shares of Resverlogix....188 million odd, lets say 200 million after a Naz IPO.  We'll say the US symbol is RXCV for fun.  This warehouse has two windows with counters where customers can come to either buy or sell shares.  Canadians go to the TSX window and order 10K shares of RVX....they're pulled from the shelves and the order is filled.   An American goes to the Nasdaq window and orders 10K shares of RXCV, the warehouse is the same one as for the  Canadian side, but its still the same shares being bought...just the four letter symbol is different. 

Clear as mud?

If the TSX listing is dropped then our RVX shares get converted into RXCV (or whatever) and assuming no  reverse split, its 1:1.