So I don't know if this anecdote helps, but I've been out of school for a few years now since I last attended—
I had to set an appointment with an administrator/registrar who wanted to discuss what I've been doing (work history, bit of life history—but these were more for their understanding than formally required), but ultimately the process for me, should I decide to move forward was:
* re-register (a quick form and small fee)
* the usual rigamarole— get my new student ID, register for courses when available, and carry on.
It was remarkably simpler than I thought it would be—even with the potential for switching programs and internal schools altogether.
I've thought about going back to finish the degree, but it's hard to see it as worth $60k/year.