I remember my friend had a 70s Dodge Dart (Slant 6 automatic) and his starter went out. His father pushed the car with his truck up to 35mph and then he put it in drive...it push started. But yeah...typically that is a very bad idea for a number of reasons. Safety being a big one...plus, on a lot of automatics the pump is driven from the input shaft...so when coasting in neutral there is often no lubrication.