I can't say that I do know how that works as I have not yet tried actually to
buy some: but on my ISA platform (TD) stockwatch, whereas the ishares Canadian ETF (ticker is FTSE:ICAN) is shown in dollars, the Australian one (SAUS) is shown valued in pounds. Or on google finance search FTSE:SAUS.
Am I going to have a problem?? The only ETF I actually hold on that platform is the ishares S&P Agribusiness commodities producers index (FTSE:SPAG), bought in mid-Jan 2013, which is going OK (+4.4% in five weeks).
....
I am about to start a non-ISA platform with HL
PS: another quick look at the SAUS spec shows it does have an ISA wrap - see
http://uk.ishares.com/en/rc/products/SAUS (and so does the Canadian one)