SWTT probably has a deeper knowledge than I but from my dealings with ACMA, Airservices and operating UNICOMS/AWIS/AFRUs etc this is what I understand.
1. ACMA does not require a licence for a mobile radio, ie hand held or vehicle fitted. Equipment certification and compliance would have to be met though. THe usual manufacturers such as ICOM would fit the bill.
2. For a fixed installation, you need to apply for a site licence. Airservices will normally assist with this process for a very reasonable cost.
3. Any person using a radio that transmits in the VHF airband 118 - 136 MHz is required to hold a Radio Operator Certificate of Proficiency these days that includes undergoing English Language Proficiency. Most flying schools can conduct this training.