Probably a little too early to get a good review on that one just yet. It was just announced at NAB, and although they said it is shipping, I don't think they are flying off the shelves in the same fashion as pre-orders of their other cameras in previous years. Don't get me wrong, I think it's a great concept and shows a lot of promise but there are some details that need to get ironed out before it becomes the "go to" camera for live streaming or event capture. For one, I think it needs a workable servo zoom lens solution, sure there are lots of options, but unlike a cinema camera, a "studio" video camera needs to be better integrated with it's lens without a lot of peripherals and work-arounds. I think a good B4 mount lens is the way to go... just need a way to conveniently power it!
In terms of whether it works with vMix, I'm pretty sure Martin has already tested the BM Production Camera 4K, so getting an image shouldn't be a problem. Using the built-in features like tally, communication and CCU functions are likely proprietary to the BM workflow so you'll need their hardware/software (TV Studio) to take full advantage. Someone correct me if I am wrong. Although I think it's a product with great possibilities, as with all BM products, it has some "built-in" limitations. Just my opinion.

Ice