you should be just fine in Switzerland.
exertion, height of climb, length of stay all correlate - but since your situation on those 3 points is mild, I would expect any problems to be unlikely or mild.
Another train situation is different from yours: when they built the long distance train across China/Tibet it exposed people to long periods up to 16,000. It was enough of a problem that it made the medical literature.
The passenger carriages used on Lhasa trains are specially built and have an oxygen supply for each passenger. Every passenger train has a doctor. China train oxygen 
