The FiST power figures are on 91 while the FoST are on 93. You can run 87, but you won't have the same power (possibly not the same fuel economy either) I would highly recommend to always run 91 at the very least. You will probably not see any difference in power between 91 and 93 except if you are tuned for it.
I run Cobb stage 2 91 because I don't think I would see the difference in power between 91 and 93, plus I'm saving a couple of bucks as it's my daily driver.
Canada has 87 octane as the minimum (never seen lower), but most stations have up to 10% ethanol in 87 and 89. A couple have also up to 10% in 91, some 5%, while some others have none (like Shell). As far as I know, the only stations that carry more than 91 is Petro-Canada (at least in the east of the country) and it's 94, not 93, with no ethanol. I've been told by a friend with a heavily modified GTR R32 that he fuels with Shell 91 as it's supposedly better quality than Petro-Canada 94.
I should give a couple of tanks of 94 with the 93 tune to see if I feel any difference. Summer is just the right time to do that.