Nice has an SIV (two of them, in fact) but they are not the same freq as “proper” ATC for IFR and CAS. Whereas in Provence, when you call Provence Info you are on the same freq as the IFR traffic in CAS. I’ve never tried to enter CAS while VFR in the Nice SIV, so I don’t know exactly how it works – i.e. whether you make the request from the SIV and they clear you and then hand you over, or whether they just tell you to call the ATC freq.
I’m pretty sure your status changes whenever you request (and are granted) transit into CAS. Even on the same frequency. The situation is the same as if you’re in contact with CAS ATC and have not yet received the clearance to enter CAS (they gave transponder and QNH but no clearance yet, you have to wait outside).
In the Nice SIVs it depends on how the SIV/ATC is being operated on that day ie are they in the same room but on different frequencies or in different control rooms.
AIUI this depends on expected traffic flow.
So one of 3 things can happen
1/ SIV will call you (assuming you are already in touch) and say you will be entering CAS in X minutes what are your intentions? You might say I wish to transit and request change of frequency to do so.
They can then come back and say “transit is approved squawk xxxx QNH yyhh” or other instructions such as not above 1000ft.
2/ You can request change of frequency to request transit and you will get the change or SIV will get it (transit approval) for you or as above.
3/ You have a flight plan and SIV will say call approach on xxx.yyy and you give your request.
There are of course other variations within these 3. There I no fixed method as it will depend on circumstances which are dynamic.
You can expect to get transit approval even though there might be limitations.
The secret is to ask clearly for what you require. Certain routings might be difficult at the time and therefore you might be asked divert little round the direct route or change altitude.
It is very important to recognise that ATS are there to provide you with a service to best facilitate your journey. They are not there to test you or to teach you how to fly.
They can however help if you get into trouble.
