For people on long distance hikes who need to resupply at convenience stores and small country stores sometimes, olive oil is sometimes not available at these places, but canola oil, and vegetable oil as well, are available at these stores most of the time. I know that's the case at the two convenience stores closest to where I live.
I'm finding that for my purposes canola oil can be a substitute for olive oil. I use it to add calories to my trail diet (canola and olive oils have the same calories per serving) by applying it out of a squeeze bottle onto Trisquit crackers. An added benefit is that it makes the crackers moister and easier to eat (I often have a case of dry mouth my first two or three days on the trail). I suspect canola oil can be a good substitute for olive oil in other trail applications too. I prefer canola oil to vegetable oil because it has no trans fats. It's even lower in saturated fats than olive oil (1 gram of saturated fats per 14 gram serving in canola, and 2 grams in olive oil). And canola oil is about ten times less expensive than olive oil for those on a tight budget ($20.00 for a 48 oz. bottle of a fairly inexpensive brand of olive oil at my grocery store, versus $1.50 for a 32 oz. bottle of canola oil).
Now, for all of you lovers of good food out there, I am NOT saying canola oil adds the same zest to foods that olive oil does. If I tried to say that I believe Mags, and certainly his family, would charge me with some kind of serious felony in food court . But, if cost is an issue, or olive oil is unavailable where you have the oppurtunity to resupply on the trail, canola can be a decent alternative.