You could be right on the money with that@Zorro and @Kifaru Bwana,
I think you guys might be reading a little too much into it. The bison are probably just in the way of construction. And the "bison plains" is probably just a fancy way of saying they are moving them to a new paddock.
In fact depending on the plans you look at, the bison (and wild horses) are potentially just being shifted to some existing paddocks that currently hold odds and ends on the other side of the river.