We have a procedure called MARSA - military authority assumes responsibility for separation. We maintain separation between the tanker and the F18 formation, providing whatever clearances, vectoring, etc, is required to get them together - usually none, they can do it themselves. When they are ready to forgo the civil separation standard, they report going MARSA and do their own thing. Once they have completed the job and are in positions or levels that we can once again accept as a civil separation standard, MARSA is cancelled and normal civil separation resumed.
That's the procedure in civil controlled airspace. Alternatively the RAAF can declare temporary blocks of restricted airspace or even temporary blocks of moving restricted airspace, but I've never seen the latter.