The RT migration is a good opportunity to explain the process that were handled via RT and now will be handled in Phabricator.
RT always seemed to me as an extremely internal-only tool. I'm not sure I really see the point in announcing we're moving away from it, perhaps unless a lot of the processes it handles suddenly become open (where appropriate)?
We are coupling a change of process and openness with the migration. Issues migrated will be restricted to WMF-NDA but vetted and made public over time. Now Operations Requests will be entirely open unless deemed sensitive. That's a fairly large change in orientation and philosophy.
I think a blog post might also be a decent venue to explain the migration process. Other groups and organizations may be interested in the technical details of how we've gone about moving separate systems (such as RT) into a single unified Phabricator instance.
A draft with raw text is available at https://meta.wikimedia.org/wiki/Wikimedia_Blog/Drafts/Wikimedia_Operations_joins_the_Phabricator_party
Your edits for correctness and accuracy are welcome. Or you can also comment here. @chasemp @Aklapper, precise data about the number of tickets migrated is welcome (if possible including open, closed, public, private, although this is not essential).
I will now start adding links and hopefully a couple of images.