Can I substitute olive oil for butter/shortening in pie crust? I was making a pie the other day -- a mock apple pie*, to be exact, which is unusual enough. But I came up short on butter and don't keep any shortening stocked in my kitchen. Desperate, I searched online for any substitutes, including olive oil, and found a small number of hits and recipes. 

I ended up erring on the safe side and just made a brown sugar crumble topping, but I've been curious about an olive oil crust ever since. Has anyone attempted it? What are some of the differences between olive oil and butter or shortening? What would be the result of using a combination of all the fats? 

* Mock Apple Pie uses no apples, and is a carboholic's dream. It was for a themed party and I don't intend to make it often. But it's quite a fun surprise to try out on unsuspecting guests at least once!
The trick to incorporating olive oil into your crust is to freeze it first until it's opaque and congealed, "like the consistency of slightly melted sorbet." From the recipe for an olive oil double crust; it has a "surprisingly neutral taste... [and by freezing it] helps the fat blend into the dough in little pockets, creating the flakiness you crave (Moskowitz, Vegan Pie in the Sky p. 39)"