Re, "Chitral is a 5741 ft runway 4921 ft MSL; can anyone run the numbers and say if an ATR 42 definitely could or couldn't get off the ground from there on one engine with the reported load / WX conditions? ".
When English is not the native language of the country issuing statements on an accident, the potential for misunderstanding is high.
The CAA statement can be taken several ways. The most likely interpretation is probably that the left engine was running (prop turning, which is the only evidence anyone except the crew, the mtce staff & the recorders will have), but had a maintenance issue. Whether that was actually the case, and if so, whether it had been signed off or not, will be eventually confirmed by the usual ways.