Theres been three power lines incidents I know of recently in Florida. Two were cats on trailers with the mast still up after the race, and the owner was moving forward to make room for others. One was at Melbourne Riverfront Park and the other at Cocoa Beach. They forgot about the power lines and drove their boat/trailer right into it. In those two cases no one was injured as no one was touching the boats, although falling masts and broken power lines certainly were dangerous.
The third case was not related to one of the Florida regattas but I believe someone was hurt pretty bad in Key Largo (caribbean club?) when they beach wheeled into a power line. Rick or Mary can confirm this I but I believe that was the end of catsailors using that facility for launching.