I've been told that Leverage is based off of the same system as the Smallville RPG, but I've never played Smallville and the person at the con was running it off of printoff from the game company - so I couldn't get an in depth look at the rules.
The game system it uses is called Cortex. Smallville and Leverage both use a specific iteration of the system that has a name associated with it, but I don't remember what it is.
From what I can gather, it mostly seems to be an attribute + skill based system where they're rated in dice. Smallville has something where your relationships also add dice, so saving Lana lets you add your Lana dice to your roll. It uses d4, d6, d8, d10, and d12 I believe. Roll the dice, add them together, compare to difficulty.
There are some other widgets, but it seems simple enough from what I've seen of it. I will admit that I haven't looked at the Leverage or Smallville versions, though.
Anyway...
Mostly, I think that you could accomplish this with declarations. I've used declarations for that in FATE games in the past. You're adding a fact to the narrative, and it doesn't really matter whether that fact is in the past or present.
So if someone has an Aspect like "hard core survivalist" the player could spend a fate point to flash back to the PC stashing survival gear in a tarp in the woods.