It looks like Survey Point, the company that currently runs the day-to-day train operations, will own a majority stake, while Carnival will keep a minority portion.
HAL and Princess (both owned by Carnival) have a huge presence in Alaska, so - for starters - Carnival wants to pick up the extra margins that the previous train owner (TWC) had been getting from bucketload of Carnival's cruise passengers.
I would definitely expect strategic use of this acquisition. Carnival could run special trains or tours for its own passengers. It certainly would cross-market its cruises to the non-Carnival train riders. It might also offer discounts or extras on cruise tours involving the train.
Disney would simply pass on the costs of the excursions (plus their own markup), so the acquisition shouldn't impact the current offerings. But, I hope this moves Disney to raise its game in Alaska. Securing a Glacier Bay contract should become a priority, as Skagway is now also leaning HAL/Princess. Maybe make (more) trips to Hubbard/PWS/College fjord.