I'd imagine they have a special agreement with Twitter anyway, at least to keep someone from programmatically grabbing @POTUS as soon as a script realized that @POTUS44 had been created.

> If they do that, then the new POTUS account will start at 0 followers (unless they have a special agreement with Twitter).

They must have made some sort of arrangement. The article states:

The account will retain its more than 11 million followers, but start with no tweets on the timeline.