I tested this in our Sandbox and it seems as if the CTA remains intact, despite removing the playbook, but I'd like to get confirmation from either product management or someone else who has encountered this before.
Best answer by sidhuView original
If you apply a playbook to a CTA and then delete the playbook, the tasks will still be there. It does not matter if the CTA or tasks are either open or closed. One change you would notice on the CTAs is that the 'Replace Playbook' option changes to 'Apply Playbook'.