Richard's comment about the tubing/timbers had me look again.
I can definitely see some wedge shaped pieces of steel under the rising track. And I can see what look like welds at the base of the steel. Thus I suspect there is some sort of horizontal steel member there. Outside of that, I DO see what looks like a piece of wood, what with the knots and such.
I do agree it could have been for clearance reasons, though it doesn't look that it is overhanging all that much. Extreme width for the car is 10' - 2". If we take the common extreme width of 10' - 8", there's 3" overhang per side, which is pretty close to what I believe I am seeing.
I surely wish I could see THAT photo BIG!