CET "System" Climate

Please advise on documentation/guidance documenting how System climate zone was created/stablished/

1. Where can we find the latest definition or implementation for quarterly impacts values for ACC combos where climate zone is System (as opposed to a specific climate zone)?

2. Is there any guidance document for supplying or updating the weights used in this calculation?

3. Is there any policy document that addresses when to submit EE claims with climate zone System instead of a specific climate zone?