I read earlier that they may have been caused by two different powerline failures. Though right now all they have is two power companies that registered failures of some type close to the same time and place the fires started. I'll try to find a link.
*edit*
Ok, found the link I read it from. I know ya'll will groan at the source, but here is where I read it:
https://www.cnn.com/2018/11/12/us/california-wildfires-woolsey-camp-hill-missing/index.html
News reports this morning are saying the Santa Anna winds may have blown power lines into each other causing sparking which would account for the utility companies outages in the CNN reporting.