Not having to repeat security for transborder would be fantastic but don't think it will happen. Works the same in Europe and Australia -- clear customs and redo security if connecting. It would also be good when entering Canada from the US if one could clear customs and stay in the secure area and not have to repeat security (especially after a long trans-Pacific flight). Air Canada used to have ground crew posted in the transborder area who could be consulted if problems arose. Now, there doesn't seem anyone to speak with anywhere up there. Very frustrating, especially if time becomes an issue and connecting to a once-a-week flight.