Is staking taking place as of December 16th 2019, 13:45 UTC?

It seems to me that it isn’t, but I was under the impression that it should be ongoing at this point.

It is! You can delegate your testADA now if you are good with the command line. Otherwise, just wait for the Daedalus and Yoroi testnet wallet releases hopefully coming soon.

You can see the ITN details on:
Then click on:
Explore -> itn_rewards_v1


Rrriiight, so ‘proper’ release – nice GUI for the average Joe – is expected later today. Ok, thank you very much for the speedy reply!