I use these camera systems all the time. It's definitely the Arri Model.
However, specifying which one is tricky due to the quality of the image provided. It may as well be the Alexa or the SXT Plus, based on the lens being used. But the layout of the buttons is hard to tell at the distance given.
I can surely tell you that it is not the Arri Alexa 65 based on the box in the front that is has is not present.
I woud also take into consideration that it could also be an Arri Amira. Another Camera system made by Arri.
Either way, I'm quite surprised Fong chose digital over film for this one. Could be logistical reasons? Pity they didn't went with Alexa 65. I hope it's the Arri XT not the regular alexa. The XT at least shoots in 3.4K but I guess the film will be finished in 2K nonetheless.
Then again, ILM is behind this so I figure the VFX will be top notch in the finished product. I hope they're going to show off some scale with the next trailer.