The canals are owned and operated by utilities. Even if they pass through a farm or whatever, they're still owned and operated by utilities. It's kinda like a sidewalk/easement: you have to maintain it, but if the city wants to come in and tear it up to rebuild, there's not much you can do to say no. And more importantly, they're not split up (i.e. one company owns a three-mile section, then another company owns a few miles, etc.); they're owned by one company start to finish between the reservoirs they connect.

It's great because it reduces water evaporation and algae growth, and the water that evaporates anyway cools the panels to make them more efficient. Plus nobody gets mad about the eyesore because it's literally an improvement of otherwise unusable space.