From what I’ve seen their dev tools internally are incredible- Facebook engineers constantly are saying that github is crazy behind and I’ve witnessed things that they can do that would make that true. Other times... they still have pretty old school hookups and getting stuff provisioned can be a pain (but if you can make a compelling business case this can all change)

Does Facebook still use Phabricator?

Yes, but it has forked so much that it bears very little resemblance to the public OSS version.