Hi there. I'm responsible for a lot of the graphics technology behind Shadowrun, particularly the shaders. Shaders make the world go round, as far as I'm concerned.
I don't know the specific answer to the polygons question, but I'd guestimate that each character is around 15 - 25 thousand polygons from 10 thousand vertices. Much of the character content is modeled at much higher resolution, then tools are used to extract detail from the high resolution model to the lower resolution model.
Shadowrun uses 2x multisample antialiasing on Xbox 360, and any supported level of antialiasing on PC. I can tell you that the game looks really nice with 6x MSAA on a NVidia GeForce 8800.
HDR lighting is such a relative term. It is easy to make your engine use "HDR lighting", but it's hard to make your game look freaking awesome by using HDR lighting. We just recently put the final polish on the post-processing systems, and I can tell you it is gorgeous in a very HDR way. The screen is dripping in HDR lighting. So the answer to your question is that the Shadowrun Engine not only uses HDR lighting - it basks in the glory of HDR lighting.
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I just wanted to correct one statement I made. I know the world revolves around high definition these days, but I forgot to mention that we use 4x MSAA when we're on a standard definition display. So you're either getting full HD with 2x MSAA, or standard definition with 4x MSAA.
more here:
http://forums.shadowrun.com/forums/thread/35154.aspx