Obviously, in the USA (and most other countries), they would treat this man far worse. Most places he would have been executed.
According to Wikipedia, there are 36 countries where execution are used in practice, another 51 there execution is not used in practice, but still on the books, 7 where it is only used for war crimes (or similar) and 103 where it is not used. Even if we assume that it would have been called a war crime and that he would be executed if there was a law allowing for such (even if it was never used in practice), then Breivik would still not have been executed in half the countries of the world. On the other hand, over half the worlds population lives in one of the countries were execution is used in practice.
With that said, while I'm not in favor of harsh punitive treatment in prisons IF it doesn't help prevent crime, nothing in the article sounds unreasonable. He is a dangerous killer - he killed 77 people. It's not unreasonable for his jailers to try to prevent it from becoming 78. He's so dangerous that making him wear cuffs when moving him between cells and preventing him from coming into proximity with other prisoners seem like reasonable precautions.
As others have noted, the crime this is meant to prevent is his murder. His crime was committed with weapons. I have not heard anything about him being especially dangerous without such.