Canadian corporations are considered "International firms" in the IBES Detail/Summary History file. This corresponds to values of the "USFIRM" variable of 0. IBES uses the convention of putting an "@" symbol in front of tickers for international companies, with the exception of Canadian companies. Therefore, if a company ticker does not begin with an "@" sign, and has USFIRM = 0 (in the sas datasets), it is a Canadian company.
Also, IBES may classify some ADRs as US only, reflecting the ADR's exchange, instead of the underlying home country. For details on this issue, you should contact IBES.