Could the experience related on p. 6 of the 2009 "Bearing Thorough Witness" About God's Kingdom book (the so-called Acts commentary) be a motivation for the cart work? It relates:
"In the Far North, Witnesses in Alaska take advantage of a unique opportunity to preach during the summer tourist season. When warmer whether brings cruise ships loaded with visitors of many different nationalities, local Witnesses station themselves on the dock with an attractive display of Bible literature in a wide variety of languages" (my emphasis).
Does anyone have any inside knowledge of whether this played a role in the cart work? Perhaps they expanded on what they felt was a good idea from Alaska?