Steps to enable the Inter-Team communication feature:
1. In the desired Teams enable the 'Create new case if recipient does not match primary queue address.' checkbox option.
NOTE: Implement this within a Test environment and confirm enabling these features doesn't cause more problems within the specific Teams than it solves, before enabling in Production.
2. Create Routing Rules for each Team that you wish to have communication between. On the Routing Rule tab ensure the 'Send Open Confirmation' checkbox is unchecked, and the necessary Case categorisations set/Template selected. On the Conditions tab ensure the To email address condition contains that of the destination Team, and the From email address condition is the sending Team.