well... imagine this - you are a concert agency, then some promoter comes, and hires you to do this hall and this artist. you do, it sells out, the room is near empty.
should you be concerned where did the money come and go?
That's entirely different because the agency is an intermediary. How can you abuse a utility service to launder money?
Even then unless legally obligated I don't see why you should care. Just report the highly suspicious activity and let law enforcement handle it. Not your problem.
They don't get in trouble because you can't abuse a utility to launder money. The onus is on you to provide an example here.
You only need to look into your customers to the extent required by law; beyond that it's not your problem. In your example with an intermediary a failure to report suspicious activity could potentially result in you being viewed as an accomplice.
Even then unless legally obligated I don't see why you should care. Just report the highly suspicious activity and let law enforcement handle it. Not your problem.