From what I can see at the WACOM website, this tablet ships with a canned ICC profile at 6500K white point. I'm guessing (since the specs make no mention of adjustable white point/brightness/contrast) that you can't actually calibrate the tablet.
You should be able to profile it like any other LCD monitor. Profiling software will adjust the LUT in your video card to attempt to linearize the display before creating the profile.
I'm also guessing that for as expensive as this tablet is, you should be able to get good results by profiling it without calibrating it first.
That's my best guess, anyway. Hope it helps.