In UK and Europe where we don't refer to L1 or L2, most, if not all e-tron charging is carried out at 230-250 VAC. The overriding factor that affects whether or not pre-conditioning will work comes down to the maximum current available at the above voltage range.
The provided Audi EVSE has the ability to switch between 50% and 100% of the maximum input current.
The EVSE can be connected to single or three phase supplies and it is the input cable to the EVSE that signals to the e-tron charging circuitry what maximum current is available.
A standard UK domestic socket will provide a maximum continuous current of 10A which can be reduced to a charging current of 5A by selecting 50% on the EVSE.
Similarly, the EVSE can be connected to a 16A or 32A "commado" type socket, single or 3-phase which will provide a charging current of 16A (e-tron maximum) or again reduced to 8A by selecting 50% on the EVSE.
I know that pre-conditioning works at 8A, 10A and 16A but am unsure about 5A.
I guess North American owners may have similar functionality, again dependent upon the input cable to the Audi supplied EVSE.