No, the tray's kinda small and has two molded in places where something would go. Thecharging cable fits under the center hatch in the floor.
My PiP isn't handy at the moment, but if you are speaking of the tray on the RHS in the rear, I'll tell you what fits nicely: -space blanket -pocket knife -flattened partial roll of duct tape -coil of cord -zip ties -large garbage bag The car isn't quite like the FJ40, sprouting shovels, come-a-longs, and gas cans, but I still try to be prepared. Now I do wish it were easier to stow the retractable cargo cover in the back without removing those two side hatches...
Like I said, "be prepared". Actually, re-reading my list it kinda does sound nefarious! But most of the time it's simply used for stuff like dirty/wet clothes or fixing somebody's pack at the trailhead--I promise. (I also forgot that there is a hand-crank flashlight in there as well.)
Besides the part that holds the cargo cover, there's two molded parts that fits something. The regular Prius doesn't have the tray covering the 12V battery.