Update to the light scattering sample is now available for download. The technique demonstrated in the original sample was capable of rendering directional light source only. This sample shows how the base approach can be extended to support spot and point light sources. Similar to the base approach, the algorithm exploits epipolar sampling and 1D min/max binary trees to accelerate ray marching. The main difference to the base algorithm is that there is no closed form solution to the in-scattering integral due to a spot/point light source. To alleviate computations, the technique exploits simple and efficient pre-computed look-up table.
The presentation from my GDC 2013 talk thoroughly describes the technique.