We demonstrated the capability on the 767, but it was never an approved procedure. To use it, the operator would have to make a specific request to Boeing, and Boeing would issue an NTO. I don't think it was ever actually done out in the real world. Basically for emergency use - e.g. there is a hurricane coming and you need to get the hell out of Dodge before it arrives but don't have a tug available.
I suspect the 757 was the same way but I don't know that for a fact.