Haidinger's brush: Is this a by-product of the eye's physics, or are there any evolutionary grounds for it?
According to the link you provided, the phenomenon Haidinger's Brush seems to be associated with the macula of the retina. The yellow color of the macula may explain the yellowness of Haidinger's Brush. This suggests to me that the brush may be an artifact of the structure of the eye, and others have claimed that Haidinger's brushes probably do not have any ecological significance (Greenwood et al. 2003). If the brushes do not have an ecological significance, then they are very unlikely to have any evolutionary significance.

The brushes may be visible to other primates, such as Macaques (Snodderly et al. 1984), as they have a macula structure very similar to the human macula. This leads me to think the phenomenon would also be potentially visible to other primates such as chimps and gorillas. If so, then our nearest ancestor (forebearer) that could potentially see the brushes would be the common ancestor of humans and chimps. 

For a broader review of polarized vision and underlying evolutionary hypotheses, the paper you linked to by Cronin et al. (2003) is a good review. I also came across a book, Polarized Light in Animal Vision. Polarization Patterns in Nature. by Gábor Horváth and Deszö Varjú and published by Springer. The front matter and table of contents are available here.  It appears to be a very thorough review of polarization vision in animals. 

Literature Cited

Cronin, T.W. et al. 2003. Polarization vision and its role in biological signaling. Integrative and Comparative Biology 43: 549-558.

Greenwood, V.J., et al. 2003. Behaviorial investigation of polarisation sensitivity in the Japanese quail (Coturnix coturnix japonica) and the European starling (Sturnus vulgaris). Journal of Experimental Biology 206: 3201-3210.

Snodderly, D.M., J.D. Auron and F.C. Delori. 1984. The macular pigmnent. II. Spatial distribution in primate retinas. Investigative Ophthalmology and Visual Science 25: 674-685