It uses VMware Tools drivers, and the SVGA II virtual graphics device.
What's cool is because it's abstracted, you can use it with or without the eGPU.
You can plug in while Fusion is running, and it will 'just work' and start using the eGPU. I demo it in my upcoming VMworld presentation, HCP1833 btw
The VM is still compatible with the rest of the VMware infrastructure, so you can move it to workstation or ESXi and not have to 'disconnect' the eGPU in the guest like you would if Passthrough were possible.
So as far as docs go it's like... 'plug in, it works'. Not a great idea to disconnect it while running (I have had it both be fine and also crash), but you can just suspend, disconnect, resume and keep going.