Absolutely they are banned in production but we don't search pockets to ensure people don't bring them. You might think that you can use a 3 strikes and your out system to convince people not to use cell phones but we have had no luck with that - we will literally just turn through employees.
Maybe it's different in your industry or location but here we're talking minimum wage jobs with a pretty decent job market for unskilled workers. I've literally had 6 people walk out in a day and get jobs somewhere else the next day. Honestly put, many of my employees wouldn't care to lose their job. (we could have a long discussion about how the company festers this attitude with working expectations, wages, and benefits, but that's a story for another day)