I think he means the airside MLL, not the Arrivals Lounge. There is a complex of lounges on either side of the entry way to T3's gates. I believe the AA one is on the main level to the right, while AC's is on the second level, but also on the right. BA has an Executive Club to the left, while their First Class lounge is to the right on the first level.

You will only be able to use it if you are flying AC or a STAR carrier on a same day ticket. It is nothing special, but as good or better as most domestic Admirals Clubs. Alcohol is free. Not sure if there are any showers, just bathrooms. There may be a small shower/change room but its use is not advertised.