First things first: the bassieres definitely did not cause the women to be struck.
As pointed out above, the amount of metal in an underwire bra is very small compared to the size of a human body. In order for the body’s average electrical resistance to be lowered by any significant amount, it’d have to be one hell of a big bra. (How big, you ask? There aren’t that many letters in the alphabet.)
Here’s what really happened. When the woman was struck, the electrical charge travelled through and across her body on the path of least resistance. Since metal has far less resistance than flesh, a lot of current was forced through those wires. This quickly raised the temperature of the metal, and the hot metal then burned the skin. (Some electrical arcing may also have contributed to the burning.)
cher3 is on the money; lightning victims tend to receive burns from any metal object near their skin (watches, jewelery, etc.). This isn’t what causes death, though. The electricity itself damages the nervous system to the point that the heart stops beating.
(Disclaimer: My office firewall won’t let me on to reuters.com. If the news story contradicts something I’ve said, please let me know.)
Laugh hard; it’s a long way to the bank.