At work I have access to servers controlling dozens of manufacturing plants around the world. All the PLCs and the control equipment are behind a local firewall with very strict controlled inbound addresses; that means I cannot interact with it from my computer, only from the server that is collecting and archiving data. This setup is approximately the standard in the industry, there are a small number of solutions everyone is using and the implementation guidelines are very clear and easy to follow. That makes any honeypot an obvious honeypot because there is no such thing as a PLC accessible from Internet in a real production site.