The more I look at the photos, the more I think the second "motor" is really a look-alike. Examining the freight engine, I see that it appears that all of its wheels have o-rings as well, though the construction of the truck is different fore and aft (or whatever the appropriate train terminology is; my apologies). Note the technic pins between the axles on the dummy. See:
http://www.flickr.com/photos/warrenelsmore...57623478006558/
I am guessing that Lego has gone for symmetry and that if these sets truly represent what is coming, both trains will have at least one non-motor bogie that uses technic axles and wheels with o-rings. In the freight train it will all be on the engine (i.e., a motor and a look-alike bogie); in the passenger train, the non-powered end of the train will be made to look like the powered end. But why use o-ring wheels in a non-powered bogie instead of the usual wheels? An expedient for Legoworld? Less expensive? Good to have more o-ring wheels for when the ones on the motor wear out?
Rob