Just to clarify ... there are two things here with regards fans and I am writing this based on my observations rather than absolute knowledge ....
The front fans are driven by engine temps i.e. coolant temeperature. On my Vee these tend to come on when the car is stationary for any length of time.
The side pod fans are driven by engine compartment temperature. I find on a hot day, the side pod fans come on quite regularly - but typically only when the car has been stationary with the engine running. IIRC some owners do not experience their side pod fans coming on and this can be related, as James has said, to faulty sensors in the engine compartment.
From what I can recall, based on a drive last night too, side pod and radiator fans can both operate with the ignition off.
Martin