The most recent version (v3) of the Mystic class from Unearthed Arcana can be found here.
All the Mystic Orders (subclasses) except the Soul Knife get Bonus Disciplines:
At 1st level, you learn two additional psionic disciplines of your choice. They must be chosen from among [your Order's] disciplines.
One psionic discipline can normally be swapped out every time you level up:
In addition, whenever you gain a level in this class, you can replace one discipline you know with a different one of your choice.
Can the Bonus Disciplines gained from a Mystic Order also be swapped out, even for replacements that aren't from the Order?