At the moment it is not possible to translate to translating back up unsubscribe and subscription update confirmation pages.
The multilingual module use for the preference page does not have an analogue on the subscription confirmation page, it would be great to implement a translation for both the pages (unsubscribe and subscription update confirmation pages).
I upvote this idea. Today the unsubscribe and subscription update confirmation pages are in French only. We are an international company : non-French contacts must deal with French content which is a problem now.
Actually no. It is possible to translate the subscription types with the new feature, and the subscription preferences page with the multilingual module.
The issue is that the unsubscribe page and the subscription update confirmation page are not translatable. It would be great to have the multilingual module for these pages.