I'd say they would be released into Canada, Iceland, Greenland, Northern Siberia and maybe even experiment and put some in the Hilamalayas. That would be my guess. But to have a living, thriving population of an animal which went extinct tens of thousands of years ago with no natural predators, might pose a problem. Sure, in Canada, you may have bears and wolves and all sorts of other goodies, but the truth is that the only way to really regulate their numbers would be to have a hunting season, whether you like it or not (unless bears prove to be a formidable foe to the mammoths). I see they being released into the wild if it goes according to plan, not just stuck in a zoo. Is there even food for them anymore? Can we bring saber-toothed tigers back as well? Saber-toothed cats? Giant sloths? Early horses?