Immi dept and state governments are aware of our visa status all the time as they exchange information.
We still paying the same tax on bridging visa as we were on 489. Centrelink has automatically renewed our interim Medicare card even though they were aware our visas just moved to bridging visa status.
You are not required to pay school fees for your son when the 489 visa expires.
The bridging visa has the same conditions as the 489....no school fees, access to interim Medicare card and sadly still ,restriction on living/working at non-regional areas/cities.