A buddy of mine bought one last summer, his 520 EXC does fit in there, but IMO two would be a bit of a stretch. It looks like it is at least a foot narrower than a standard full size because of the storage bins on each side, and it is also at least a foot shorter than a normal short bed. I'd say its payload size is about that of the average short bed compact p/u.
Maybe they sell them w/out those side bins, if so I think you could wedge two full size bikes in there.