For successful SCAMPI appraisals, is there any reason to prepare process compliance at the sub-practice level? Would appraisers be looking for evidence at that level?
This is a question answered by taking the 3-day Introduction to CMMI class and also by your Lead Appraiser. There are three CMMI components: Required, Expected, and Informative. An appraisal only covers the Required (Goals) and Expected (Practices) components. Your Lead Appraiser should also be providing some training or guidance on how to build the PIIDs, which contain the objective evidence for an appraisal. And the whole appraisal team is involved in reviewing the PIIDs during the Readiness Review to determine if the evidence is proper for a SCAMPI appraisal.
If a Lead Appraiser or the appraisal team is appraising you to the sub-practice level, they have gone too far. The SCAMPI method is only concerned with appraising the organization to the Goals and Practices.