I listened to some of this transpiring on the radio...LAFD and LA Department of Water and Power were pointing fingers at each other. DWP said there had been no vault explosions....which was correct. The explosions were produced by the gasses from the slow burning cable igniting at different sources on the street.
The media reported initially that both firefighters were felled by flying manhole covers...which I thought was nearly stastistically impossible....turns out none of them were hit by manhole covers.
Thank you BurbankKarl for the update and feedback.