One would think that the President's team would travel with a known-good pico-cell device and let his phone only connect to that. Or force wi-fi calling and only let the phone connect to the wi-fi network they bring along everywhere.
This doesn't prevent the other end from being surveilled, if indeed the signal is being intercepted. Similarly, keeping his phone malware free doesn't solve the problem of his friends' phones getting compromised. So without both ends on a secure line there is no real good way to secure things. Those listening in, as suggested by the paper, do not necessarily need to intercept every call. Sure they would love to listen in on every call, but it is not necessary if they just want to get a better model of how he thinks.
There is a huge amount of unwarranted assumptions and misplaced trust in the President* to follow the advice of his team in this thread. He has made it very clear that he thinks he is the smartest person in the world and doesn't need to listen to experts.
I don't think anyone can follow him with a known-good device and let him connect to that. The article describes his short-temper and complete unwillingness to sacrifice even a few minutes to take care of security issues.
> Or force wi-fi calling and only let the phone connect to the wi-fi network they bring along everywhere.
You cannot force this President* to do anything that he thinks inconveniences him. You can't "force WiFi calling" without being fired or at least being afraid of it.
The solution here is not a technology fix for the phone of this President. The fix is a new Congress that cares about national security and a new President that cares about national security.
Also,
> One would think that the President's team would...
No, one really wouldn't. The President's team is not concerned with actually fixing this problem. They have made it clear that national security concerns come second to the whims and desires of the President*.
Nothing in the schemes I suggest takes the President any time. You outfit his environment with picocells & secure wi-fi networks, set up his phone to prefer to connect to those, and you're done at least for preventing Stingray attacks.
I think a more compelling answer would be "You'd think that the government's IT people would have found a way for Hillary Clinton to have an easy-to-use yet secure email server and yet they stonewalled her to the point that she had her own server set up at home."