Legal Question in Real Estate Law in California

There isn't any specific code, it is simple trespass if they don't have an easement to do it. Unfortunately they probably do have an easement burried somewhere in the title to your property. Might be worth having someone who knows title an easements take a look for you though. If they don't have the proper easement for the location they placed the wires, you can force them to rewire.

I agree. Your starting point here is to check your title to see if it indicates where the utility easements on it lie; sometimes they are identified in your title insurance (and they should be).

In my experience, PG&E is very fussy about having a proper easement under their wires, and will not string a wire to someone even if it only crosses a few feet of a neighbor's property where they don't have an easement. Due to a three-foot gap on property where the owner wouldn't give an easement, my neighbor had to dig a 700-foot trench (partly on my property, and I did give him an easement) to bring an underground line from another power line on the other side of his property.

I suspect the cable companies are a little less careful - lower voltages and other reasons - but note that most utility easements are for the benefit of all utilities, not just electric power or the first utility to arrive.

They have easements. If you want power, they ask you to grant an easement. You are most likely wasting your time, but if you want to make an issue out of it, they can cut power to you and your neighbors property.