Experienced men (older) generally don't bring the phone into the shop. they know better.
the issue would be with younger apprentices or rookies who enter the shop environment and are not acclimatized to the various dangers of the area.
the only advantage would be having multiple calls to 911 if something bad happened.
The economy is kind of taking a down-swing in the oil sector, and guys who want to keep their job and help the company maintain a high safety rating wouldn't challenge a cellphone rule.
We have PTZ (pan,tilt,zoom) covered globe cameras in our shop where our safety manager is able to conduct surveillance of unsafe work practice from his office. if he sees someone repeatedly performing unsafe acts, that person is brought into a meeting, and confronted with the unsafe practices, and then shown the video. Based on the severity of the safety violation, the guy could be suspended without pay temporarily, assigned other duties, or terminated.
you have to develop a safety policy regarding cellphones and unsafe practices, and establish a system. a company losing it's safety rating can be incredibly injurious to finding more lucrative contracts these days, no matter what industry your manufacturing facility caters to.
I strongly suggest video surveillance to avoid situations where the employee tries to file lawsuits for unfair termination or something to that effect. When it's life or death, you can't afford to be lenient.