To access render hair data, use CRenderHairAccessor to get the render hair data. Then either save the data on disk, or put the data in a userdatablob and pass it to the shader.
See the Wireframe example in the Softimage SDK workgroup for an example of how to use an operator to pass a UserDataBlob to a custom shader.
Existing (pre-5.0) shaders that accessed hair data must be rewritten to use CRenderHairAccessor.
Autodesk Softimage v7.5