Loke’s original question:
“When can pilots legally/safely abandon a S/E procedure? I realize that pilots cannot accept vectors from a controller – at least initially – when performing a Special S/E procedure. The question is – when can a pilot accept a vector (and altitude assignment) from a controller?”
These engine out procedures are conducted on the Captain’s Emergency Authority. This is what allows us to deviate from ATC instructions and/or departure instructions. This means you do whatever is necessary to ensure safety of flight. Once that is accomplished it is the Captain’s decision to continue the procedure or return to ATC control. If the emergency is under control and you are above the MVA why not accept vectors at that point? It all comes down to judgement.