Any part of KKH between Islamabad and Gilgit (including Babusar Pass I think) is subject to delays due to need to travel in convoys with armed escort, unless you have a personal armed police officer travelling in your vehicle - this is usually available to people travelling with a licensed GB tour operator, according to my experience when travelling both ways up and down KKH in late May-late June, prior to recent terrorist attacks in Nanga Parbat base camp. Could be more difficult now, but can't confirm one way or another as am now back in UK. However, that was my understanding prior to 22 June. Maybe someone travelling from ISB to Chilas after that date can update on my info? For myself, I would say - no, not safe!! Don't go there!