It is possible to touch walls, ships and anything else with B2, but only at a very low pace. In real life, would you thump a wall at greater than 2knots in something that big without causing damage?
If you are pushing up on a latitude to assist in a berthing though for example, you must ensure that you do not slide along the hull - when you make contact, make it carefully, and when you are pushing, do not allow your tug to slide, or you will cause damage. I am aware of quite a number of users on multiplayer who will not allow others to push on them since they think they will get damage, where infact that need not be the case.
Traddles: since she's a tractor tug, B2 would be best suited 180 degrees around for that kind of tow, so that the propulsion is at the stern - it helps towing quite a bit
-Alex