CS6 always uses the Lab values for spot colors to get better cmyk conversions for your output intent if you are converting to process. This has no effect on the separations other than to change the cmyk mix depending onthe output profile. If you don't convert spots to process they will continue to generate a separate plate for each spot, and if you do convert, the mix will be the best calculated mix to match the spot color for the ink/paper combination specified in the destination profile you choose.
If your job is process CMYK use the Pantone + Bridge libraries they have CMYK definitions.
The Solid libraries are for spot color jobs, Lab is the correct color space for spot colors