Earthing Gensets (Revisiting Thread �8929)

In previous post http://cr4.globalspec.com/thread/38929/Should-Mobile-Power-Generators-be-Grounded garth refers to a paper (http://www.wtia.com.au/pdf/TGN-W-05%20Earthing%20of%20mobile%20generating%20sets.pdf) that states to not fit an earth electrode to the mass of earth on portable gensets. This makes the genset functional earth connection 'floating', and an IT earthing system. (?An IT earthing system still has a connection to the mass of earth at the load side of the installation.?) Can someone please help me learn why?

I am trying to apply this (in Australia) to a specific scenario of a vehicle mounted genset (240v single phase, 16KVA). Each circuit is controlled by a double pole switch and protected by a GFCI. The earth conductors are bonded to the frame/chassis of the vehicle. Of primary concern is the potential harm to a person in the event of a fault if they are standing alongside the vehicle and they complete a circuit to the ground upon which we stand.

Possibly I just do not understand any of this, but not from a lack of trying...