I recall a massive blow down in the Alpine Lakes about 20 years ago that blocked large portions of the Icicle Ridge(?) trail. When the local USFS land manager sent crews up to clear it with chainsaws the following summer, ALPS threatened to file a lawsuit under the "motorized" (actually, mechanized) prohibitions of the Wilderness Act that you mention. Fair enough. The USFS manager, following the letter of the law, instead sent his crews in with hand drills and DYNAMITE. ALPS promptly withdrew their complaint.