I never really got into Half-Life/Source mods as I felt the engine was a little bit too limited to tell grand stories - which cyberpunk style games tend to have.
I came across another Cyperpunk game today, this time of the interactive fiction genre but for PCs, and it's rather new!
It's not quite Net Gain, as it has flying cars, but it seems rather dark and otherwise rather fitting.
http://www.cabrerabrothers.com/