I just got off the Odyssey, Chromecast was available.
You select 'streaming services' on the Home screen of your cabin TV, it then gives you url and a code that you need to open up and encode on your device (phone, laptop, ...). Once done they give you the Id of the Chromecast associated to you and it opens up on the TV.
I might be mistaken but it doesn't look like the chromecast is in your tv, it looks like it's somewhere on the network, when you open up that url it gets somehow associated to you and the tv, the network access gets opened, you are then able to see it on your device, and it pops up on the tv.
(everytime you do the process you get a different chromecast id, if you do it in quick succession you end up seeing for a short period of time all the ids on your device)