1. Opened Test Project
2. Set the Baseline B1
3. Assigned B1 as Project Baseline
4. Changed several Id’s with the Client tool
5. Scheduled the Project to see variance with baseline
6. No Change in Dates or Lines
7. Copied and Restored baseline B2 to check Activity Id’s
8. Same ID Changes are noted in B2 as the Original Project.
Conclusion = It would seem safe to change Project Ids after the Baseline has been set and assigned.
This test did not address the possibility of Multiple Baselines recorded but not Assigned.