That's sounds like quite a trip. When I first saw your post I thought you must be nuts to tke something like this on on a motorbike but then read you'll have a 4x4 support vehicle along.
I lived up in Iqaluit for a few years and experienced a few storms that came on very quickly (even in April) where I could not even see my hand in from of my face (no word of a lie).
I'm sure you'll be OK with a support vehicle and pelnty of survival and communications equipment. I've gone on a couple of 400+km trips on ski-doo in the arctic and as long as you pack for it then things are generally OK.
I look forward to the ride report - I'm hoping to ride the Dempster sometime this summer. Good Luck!