Under the same law, if the company has a policy that only approved devices are allowed then connecting your phone to the mail system is also an offence.
Nobody wins in this scenario. Yes, you can have the administrator (or company) prosecuted for breaking the law. But they will end up showing the police that you also broke the law.
I suspect that the CPS is going to be very upset if many such sets of cases come along, as they'd probably rather be spending their already limited resources dealing with something like violent crime...