Evans v Monarch is the case that often gets cited here, though it does not set precedent. The upshot is that lightning damage may well not be considered Extraordinary Circumstances, however the Pešková case (which relates to bird strke) gives another side. So yes, a bit of a grey area, and there is no point pursuing BA. But CEDR can take the wider story, which includes the oft forgotten clause of "all reasonable measures", in terms of BA reducing the disruption to you to the minimum. You wouldn't have anything to lose, there is no charge for using CEDR.