We have a policy. No phones no texting during WORKING HOURS. We had to change it because people were stepping inside the office area, thinking that would get around the "no phones in production" rule. Same with stepping outside.
I've worked in a few offices with similar policy - though mostly out of security concerns (taking pics of client info etc).
I ended up mimicking the teams Bluetooth names and sending pics. If the pics were accepted, we knew who was using their phones and gave them a warning. Some thought it was harsh, but it worked.