Back in the early '90's the firm I was working for, Logistics Systems Engineering, Inc. (now defunct), was engaged by a national rail carrier to explore the possibility of radically overhauling how freight cars (and eventually passenger cars) could be moved over the nation rail system without human intervention by using what you are calling M2M, especially intercar communications and sensors. I think this is probably a big area for M2M as is using similar technology to get drivers out of the driving loop for automobiles and over-the-road trucking.