In colour science CCT is derived from xy. xy calculation depends on the colour transform, raw to XYZ. This transform is not one-to-one because raw data isn't colorimetric. Different companies use different colour transforms for the same camera model. Say, the camera and ACR report different CTs for the same shot.
Your best bet is to shoot a camera at each CT setting, compile a table of CTs vs. wb coeffs, and interpolate.
In colour science CCT is derived from xy. xy calculation depends on the colour transform, raw to XYZ. This transform is not one-to-one because raw data isn't colorimetric. Different companies use different colour transforms for the same camera model. Say, the camera and ACR report different CTs for the same shot.
Your best bet is to shoot a camera at each CT setting, compile a table of CTs vs. wb coeffs, and interpolate.