In certain parts of the North of Spain, Zamora, leon, Galicia and Asturias, people have coexisted with wolves for hundreds of years. Farmers have huge mastiffs to protect their livestock and some even use donkeys to ward off the wolves! We have a healthy population of about 2000 wolves and the Wolf has just being declared a protected species and therefore cannot be hunted.
I love the whole rewilding concept. Lynx I think are an easier sell. Wolves when introduced initially would be quite localized. Once they start spreading though, could cause issues. Already see that with beavers having to be relocated. Re-introductions can be good if done well. If done badly they ruin any attempt to continue with that program. Yellowstone is massive compared to cairngorms national park.