Is it a seamless switch between SIM data and shared data?

I have a SIM which receives 200MB of data each month as part of a promotion 2Degrees offered early last year. I use this on a Wi-Fi hotpot. When that 200MB is exhausted, the hotspot then starts using shared data from my plan.

I think I have experienced that when the 200MB runs out, I have to reboot the device before it then starts to use my shared data.

As I soon will be streaming my wedding and don't want the stream to be interrupted, can someone please confirm that that's the case, that if data belonging to the SIM runs out, I then must reboot the device before shared data will be available to it?

Thanks.