If the attack itself was not particularly effective, perhaps that wasn't the intent. Heck, perhaps some "security consultant" who could charge the utility a lot of money for a security audit of their facilities is drumming up business without causing any significant disruptions and without getting caught?

I read one report that said the shots were placed in such a way to avoid causing any immediate fires or sparks from the transformers, and just create holes to drain the oil inside. That way, drivers along the freeway in the distance would be less likely to notice anything and call the authorities.