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How the source affects the illumination depend on only the illumination model that you use and not if you use ray tracing or not. You can have surface scattering with or without ray tracing.

Then show us an example of scattering without raytracing. You can get the buddha model i used here:

http://graphics.stanford.edu/data/3Dscanrep/

Or use whichever model you feel is appropriate.

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• IBL is also a fake method, the reason is that the illuminantion in a point not only depend on the intensity, it depend also of the angle of incidence. The image used mapped on the sphere or other shape only contains the intensity information with no angle information, that would be impossible to be stored.
  The equivalent of IBL in games are the light maps.

Light maps have nothing to do with IBL. They are just stored maps for any kind of lighting. You could store IBL in them or direct lighting or occlusion or whatever. IBL is calculated on the fly each frame by casting a hemisphere of rays around each surface normal and averaging the result. I thought you already knew about this as it is clearly explained on debevac's page.

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-  Ray tracing is unable to do a correct ambient or global illumination, in theory it would be able to do it, but the required computations would last forever.
The only way to do a correct global illumination is with radiosity, then you can use if you want, the radiosity generated maps with or without raytracing.

You dont know what you are talking about. No one uses radiosity in its primitive form, that is the most inefficient and limited way to do GI. It is slow as hell, doesnt handle point lights properly and cant do optical effects at all. Most apps use other better approaches like monte carlo GI or photon mapping. Or they use a combination of IBL and photon mapping. About the only commercial app that ever tried the primitive approach was Lightscape for MAX, and even they folded up due to competition from superior systems in VRay and Maxwell.

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• Raytracing is unable to handle particles, smoke, clouds, fire, etc must be done by other means.

The technical term is ray marching, it is a modified (more complex) form of raytracing:

http://graphics.ucsd.edu/courses/rendering/2004/gmromer/index.html