See
this link to a recent thread discussing a similar subject.
I think we agreed, in that thread, that while the C208 falls under the SE Class rating, it belongs to a small group of mostly turbine aircraft which CASA requires flight training and a flight review (so not a type rating and test, but similar) in order to exercise the privileges of your SE class rating on these particular aircraft. After that you just have to do the AFR on ANY SE class aircraft to maintain your privileges.
So, no, it is not as simple as doing a GTE groundschool, although if you don't already have GTE, they will have to cover those principles during the C208 ground school/briefings. You will then get GTE endorsement on your Part 61 FCL, but not a C208 endorsement/rating as it falls under the SE Class rating.