Comment 25 for bug 365458

Maybe I misunderstand what this means then:

"14.3.6 Clipping paths, geometry, and pointer events

A clipping path is conceptually equivalent to a custom viewport for the referencing element. Thus, it affects the rendering of an element, but not the element's inherent geometry. The bounding box of a clipped element (that is, an element which references a ‘clipPath’ element via a ‘clip-path’ property, or a child of the referencing element) must remain the same as if it were not clipped. "

In the browsers at least, it is interpreted to mean that although the area outside the intersection is not rendered, it still receives pointer events.