First, you need a lot more in-depth. Run the survey by people who do this for a living. You are missing a lot of information. Look for what would be the next question and try to determine if you have any biases in your research.
For example, my company's personal device policy is based on safety more then security. I work for an EPC company and people jinking with devices while working in a construction site might put an eye out (literally) or worse. Let alone accidentally dropping a cellphone from a great height, into concrete, into nuclear containment, into turbine, etc... we have issues with people texting and driving... a crane, forklift, yard dog, etc... These can be bad things. The security and productivity fears of most management is nothing compared to the fears we face in the heavy industry environment. Ever want to explain to a customer why the multi-million dollar turbine was destroyed because someone dropped their cellphone into the system?
We also have security issues, such as SUNSI information. Just don't whip out the phone and start taking pictures willy nilly and we will be fine. If not, have fun with your talk to the nice guys with the guns.
Productivity / control is our last worry. Someone will usually get a talking to if it is really egregious, but usually we don't care if you are getting the job done. The manager who does usually gets a talking to... That said... don't take a picture of your rear on a bucket and post on Facebook about how you don't do any work on the construction site... might be career limiting. Seriously...