Maybe this task is moot, but I'd rather ask in advance.
We are seeing the amount of email notifications that @flimport can create indirectly when assigning/CCing users on tasks based on the short active live that fab.wmflabs.org had. If we have exactly the same setup for the Bugzilla migration, we might end up spamming users with literally thousands of emails.
Is this assumption correct? If so, we'd better take measures.
The ideal solution would be that the actions of @flimport (and/or its Bugzilla and RT equivalents) would not generate notifications, but I'm not sure how simple would that be.
A simpler option would be to set in email preferences by default for everybody (or at least new users):
Ignore - A task's subscribers change.
This way we would save the biggest source of spam to new users, and everybody would be able to decide if/when to activate them. The noise created by the bot for "Assigned To" users is a lot smaller, and that information is more relevant in any case.