I believe you refer to Krimml Falls -
I am not certain that trips go there in winter but it is best to contact a travel- bus compamny in mayrhofen
Probably many less trips in winter but still some offerings.
They have been in business for many years - now with a big garage and office just oustide of Mayrhofen. I think that they still have an office on the main street too.
I know that they have trips to Salzburg and other places in the winter-
Carnival in Venice too.
Check their website
www.christophorus.at or csall them.