Moving from government research to academia
I can only answer for the situation in Germany (where fixed-term full professorships indeed exist). There are two different situations:


In engineering your route is basically the default route to a full professorship. You do a PhD, go working in a company for five years or more and then apply for professorships. (You may also do a postdoc before working at a company.) In other fields it is not very common to return from outside academia (the only field I know for sure is mathematics and there I don't know anybody who returned back to academia).
For professors at "Fachhochschulen" (often translated as universities of applied sciences) it is similar but not only for engineering but also for other fields. Do a PhD, work in companies, apply for professorships at Fachhochschulen. In fact, for professorships at Fachhochschulen it is even required to have working experience outside academia. However, Fachhochschulen are not exactly research institutions but focus more on higher education in science and technology, preparing people to work in companies. For example, they do not grant a PhD (but this may change in the future).