If they are itchy from insects or so on they will rub against anything solid that gives relief, including wooden fences.
If the fence is wimpy enough then they MIGHT knock it over, but it's not really that hard to put up strong enough ones. 8" posts 2 feet deep well rammed usually don't go anywhere!
As for escape, some cows are better than others!
The herd of Herefords we had when I was a kid would get through 6 strand barbed wire like it wasn't there.