Engine anti-ice, which is perhaps a somewhat misleading name, does not affect the fan blades. It is not uncommon for ice to form on the back of the fan blades in cold and humid conditions. This will happen after engine shut down where condensation will form and eventually freeze. Engine anti-ice will not prevent or remove this. The fan should be checked before start and any ice removed. If fan icing is suspected during taxi the ice shedding procedure must be used. Most aircraft also have a requirement for engine run-ups at specific intervals when taxiing in icing conditions for this very reason.