We were on the tour in June and the bus driver handed out the regular plastic water bottles. Unless something changed in the past two months, I don't think you will need to do anything special. We always refill them throughout the day. There are plenty of refill stations in all of the parks.
We had received one of the metal bottles a few years ago in the Canadian Rockies. This time it was just normal plastic bottles. I assumed it was US versus Canada.