Sorry I've no idea what you're talking about...
A subrect on a texture has an absolute position on the image.
The sprites origin doesn't have anything to do with what you do, with the subrect, it just knows that it has to put the image you want to draw (x,y) much away from where you set the position of the sprite.
Also why are you interested in knowing what SFML 1.6 does, if you're already using SFML 2?