>One source says the presidential BlackBerry can only connect to a secure base station, which can be used to hide the IMEI-number of the device and thus prevent tracking it.

So they ran into the problem facing regular people and decided to carry around around a private cell tower to fix it.

How is current presidential iPhone getting secured?

Is this only for Democrat presidents? It's well known that Trump used his personal phone, an "old android" well into his first term. There's conflicting reports out now, but one says he still uses his personal iPhone.