not sure if a mac uses the same files, my guess would be no, but no real clue =P

as for importing, i think placing the files in a folder for carrara to see is the only way
poser, along with other 3d software i used, was the same way, and saw the shader
file when the program started, adding it to its library, unlike models whic you could import

import is more for loading information from other software, so doesnt surprise me that
C5 shaders arent in the list, while models, which are in formats many apps use, are listed
problem with doing this to shaders, is every program is different, 1 shader in poser6,
no matter how simple, can't be remade 100% in carrara, and while carrara allows you
to import scenes with shaders, the shaders don't get translated to perfection
thus the reason to make shaders from scratch in the rendering app, same for lighting

using import for carrara shaders is kinda dumb tho, just drop in the correct folder
to start with, and library has access to them all, 1 click away