They were probably down last year to get the track ready to accommodate the new bobsleds. With the track updated, they can begin testing the new sleds.
We're here now and just had someone from housekeeping in our room who told us they were also doing structural repairs during this time as apparently the Matterhorn has been sinking for years.
I'm sad to see them go. This is one of my 4-yr-old's favorite rides because she gets to snuggle with me in the vehicle...Worse yet, it won't be up again until after our APs expire. That's a long refurb, but I guess structural fixes take time.