How to account for emissions
The National Greenhouse and Energy Reporting Act 2007 (NGER) is the national framework for companies to report on GHG emissions, energy production and energy consumption.
The reporting is based on how transport emissions are treated in terms of Scope 1, Scope 2 or Scope 3 emissions. The definitions of these are found on the Clean Energy Regulator site. 
The burning of fuel in fleets is categorised as a Scope 1 emission and so vehicle fleets are captured in this reporting method. When moving to electrically powered vehicles, vehicles will move into Scope 2 emissions.
The Australian Department of Energy and Environment publishes the National Greenhouse Gas Account Factors each year.  The calculation for Scope 2 emissions are based on a “factor” calculation based on the carbon intensity of each state grid. These factors are outlined on page 19 of the July 2018 report.
To the extent that local solar generation is used, these factors will be offset.
Lifecycle emissions 
The sum of the emissions from the various stages in a vehicle’s production, operation and disposal are often collectively referred to as lifecycle emissions, which include emissions produced from the manufacturing process, for both the vehicle and its fuel and from transporting the vehicle to the location of its first point of sale.
GVG calculations do not take into account energy and emissions from the vehicle manufacturing processes, due to difficulty in getting this data constantly across all vehicle makes and models. Therefore the energy consumed and emissions over a vehicle’s normal lifecycle occurs during its operational phase rather than its production and materials are used in its algorithm.
You can download the calculation of lifecycle CO2 emissions for Light Vehicles (for GVG) October 2018. It covers the factors and calculations to determine the final CO2 emissions in g/km.
Read about the types of vehicle emissions and emission standards in Australia.