I cannot, for the life of me get CUDA working. Tried in Premiere CC 2015, AfterEffects 5.5 and Premiere 5.5
Open CL does show up but there is no option for CUDA in any of them.
I also tried CUDA Z (the GPU Z similar program) and it doesn't find any CUDA cores either.
OS X recognizes the card fine.
Here's all the system info etc:
Mac Pro 3,1
Mac OSX - 10.11.1
Nvidia FX 4800
Nvidia Driver 346.03.03f02
CUDA Driver 7.5.21
I would not worry about that. The video card is such a dinosaur, so terribly slow, that you are probably better off in software only mode.