I've always been able to see it through mountains. It's almost as if there are small holes in the terrain, and once the sun hits one of these holes then the whole thing shows. It will kick in and out randomly while driving next to a hill or mountain that is between me and the sun.
Another thing I've noticed is that if there is a hill between me and a base, I can see bits and pieces of the base terrain through small 'holes' in the ground textures. A picture is worth a thousand words, and I've circled in red some of the base terrains that I see through the hillside.
I don't seem to recall the base-through-the-hill issue being present until I upgraded from an Nvidia 9800GTX+ to an ATI 5830 video card, however the sun poking through the hill/mountainsides has always been a problem.
I can't pinpoint any specific map or base this occurs at.. it just seems random throughout everything.
