'Most of those cow tags are for the last few days of the season. Is it possible that once the shooting starts, the cows head to Rimrock and Cowiche?'
Yes, that's just across the river.
If they want a dependable, predictable harvest success rate, why do they not allow the cow tag holders to shoot until Wednesday? If you want the cow kill to be on target for herd management goals, you would have those cows die on opening day IMHO.