I can say the cutting the tires in half through the steel belting is a real chore. Be prepared to tear up some saws-all blades and spend some time grinding the frayed wires so that they are not so likely to stab yourself or the fish.
Maybe there is a better way to cut the belting, but they are not friendly to the blades, I would guess that they are some sort of hardened spring steel. If you could stomach the fumes from using a angle grinder and a cutoff wheel, you might make better better time and spend less on equipment.
My biggest concern for using tires in the pond is keeping them from wondering off. Drill plenty of holes in the side walls. If not, the natural production of gaseous bubbles will fill the sidewalls and they will want to float. Tires without trapped air will sink, but they will still have some buoyancy and will move around on you unless they are staked or heavily weighted with concrete or rocks.
