RE:NYSE vs. Toronto exchange Same deal as with the Canadian shares on the OTC: the market makers purchase shares on the TSX and then sell them via the OTC. With WRN, the market makers can purchase additional shares on the TSX if need be or just utilize existing stock in inventory to accommodate trades on the NYSE.
You can convert WRN @ the forex rate to determine the respective prices, however, the last trade of the day in Toronto may be a retail buy whereas the last trade in Manhattan may be a retail sell, which could equate to a few cents difference depending on how greedy the market makers may or may not be on any individual day with their spreads.