I bought the pannier set last time it was on sale - it looks pretty much the same as this one, though there are some minor differences. I can't tell whether the attachment system is the same, however.
On the set I have, there are no catches or bungees - instead, there are a series of velcro fastenings. Difficult to describe, so I've attached a couple of pics (with apologies for the bad phone pic - need to charge my camera battery!).
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As you can (hopefully) see, there are 3 velcro fastenings down each side, which strap round the legs of the pannier rack, and there are two more velcro loops at the top of each side which fasten to the top of the rack.
I'm afraid I haven't got on with this attachment system - the whole thing moves around a lot, as the velcro doesn't fasten very tightly. Because of this, the panniers have to be loaded fairly evenly - once I made the mistake of putting my lock in the top bag without anything in the side bags, which made the panniers swing from side to side too much for my liking!