I don't know how it works up there, but we have a similar program at Alpine Meadows. It more or less runs under the auspices of the Volunteer Ski Patrol, but not really. We have 1st Aid at Alpine, but no clinic (Squaw on the other hand has a clinic with paid docs in it, and can treat patients - we ship them to the hospital for x-rays or any real treatment, and we don't dispense meds other than tylenol/advil).
Like Ski Patrol, its a volunteer program. The docs will sometimes be called to a wreck on the hill, but more often than not, just meet us (patrol) in first aid if we ask for them. They'll do some basic things like re-set a dislocated shoulder if they feel its advisable, or clear someone to be released from a backboard. They really don't render treatment, and as I understand it, their liability is covered by the mountain as long as they are on duty.
The docs are not trained in handling sleds so if they're first on scene at a wreck, they invariably call ski patrol for packaging & shipping services back to 1st aid.
The docs are great to have on the hill. Mostly its a pretty laid-back job for them and they enjoy the same benefits as ski patrol, without the physical demands or hill-prep and maintenance responsibilities. They don't open the hill and they don't do sweep so they don't have to be on duty until the lifts open to the public, and they're done at 4 when we shut down. I think that patients appreciate getting a "real doctor's" opinion on some injuries, rather than just patrol or the nurse in first aid. I know that when I tore my achilles a few seasons ago, it was nice to have a doc there to give a definitive diagnosis, and to tell me that I would be fine waiting a day to see my regular ortho, rather than having to deal with it immediately at the local hospital.
I assume they also enjoy the nice tax benefits of contributing your time to a non-profit volunteer organization, but I'm not sure of that. Volunteer ski patrollers get to deduct ski-related expenses from our taxes (e.g. ski lease, mileage, some equipment). But even without the tax benefits, free passes for the family isn't a bad deal. And I think we even let them use the ski patrol lift line.