Dick - As I understand it, the BUK has a radar controlled proximity warhead, which strikes me as being what you describe. There are people who are far more qualified than me who could no doubt go into greater detail/correct me.
TC - I agree the airlines that continued to use the routing over eastern Ukraine after the AN26 had been shot down were utterly irresponsible. I know about the IL76 being shot down in June, but thought it was a fair bit lower and could have been done by a MANPAD. Do you know more about this one?