I would vote against the BRP Modulars for extreme cold weather. Year before last I bought a mod-1 that I love in general, but it has its issues in below zero weather.
Last year I got frostbite twice on evening runs around zero or below. This was on my cheek above the mask, not inside the mask as I've heard some other experience. You really need to cover almost all exposed skin in these situations.
Also, when it approaches this cold I find the condensation starts to build up and freeze in the vent tubes where they exit the helmet. A couple of times it got to the point of blocking air flow. I'd have to stop, take off the helmet, and try to break out all of the ice. Tough on the hands in the cold, too. Swapping a mask as someone above noted might help, but I found the ice would block up the port in the helmet shell too and that part was really hard to clear and a new mask wouldn't help. A buddy who has the mod-2 experienced less of this than I did, so the mod-2 may be improved over the mod-1, but he still had some issues.
I've had enough issues that I'm thinking about getting a different helmet to wear below about 5 degrees, so I'm interested to see all the responses you get.
Don't get me wrong. Above 5 degrees I really like the mod helmet. Very comfortable. Never fogs the helmet lens or my glasses. Flipping up the visor alone or the full face is easy to do with gloves on. Ventilation adjusts well, etc.
Good luck. Wish I could do the Alaska trip.