PH,
Keep in mind that every unit and every state may be completely different, but in the area we hunt, the bulls do in fact rut near or in the calving areas. The reason being is that the cows come into the calving areas in early spring, where there is plenty of feed and water, they have their calves and spend the summer there. The bulls head up high in early spring, following the snow line, feeding on the first shoots of grass and buds on the brush/trees. They stay up high all summer, where it's cooler and the bugs don't bother them while their antlers are growing.
When the rut starts kicking in, the bulls will come down in search of the cows and calves. They will spend 2-3 weeks rounding up the cows and establishing their herums. Then, from what I've experienced, they will move back up into the higher country with their herds, away from the rifle hunting pressure. Then the snow starts flying and they move into their wintering areas, and the cycle starts over.
We scout our areas by finding the cows in the spring/summer, we rarely see bulls while we are scouting. But by the end of August, the bulls are right in where we saw all the cows during the summer. I hope this helps!
Corey