Don’t let mobile malware steal your company data

not allowing rooted or jail-broken phones?

"it is reasonable to enforce a company policy of not allowing rooted or jail-broken phones onto work premises."

A) Why is it reasonable?

B) What risks does it prevent? (in particular, risks that are not present with a factory-original phone?)

C) How do you expect it to be enforced?

D) How significant is the risk?

There'll often be easier options anyway. At a secure (UK MoD secrets onsite) establishment I'm familiar with, you just have to come in looking like a plausible printer/copier technician. No one will know or care who you really are (neither IT nor Facilities maintain the printers, it's outsourced), no one will be able to check who called you in, there will always be kit needing attention, and of course it will be networked and you will be allowed in with a laptop which you can plug in to the networked printer. And printers are full of nice dark corners where you could easily hide something the size of a Raspberry Pi.

The "security" people on that site have been notified of this hole. Apparently they get quite upset if you don't provide their required four weeks notice for the usual class of visitor, but have no suggestions or concerns when there's a gaping hole in the organisation's procedures. They will, one day.

You don't need to weaken GSM to give government access.

The government has the right of legal intercept. You can build all sorts of things to protect yourself from organised crime, business rivals, tabloid newspapers whatever. But there is no protection from The Government.