Not a CFM operator, but with an engine which does suffer fan blade icing in freezing fog. Frequent N1 increase on the ground, and if applicable in the air, shed the ice without problems.
However, there have been rare instances of engine damage caused by intake ice shedding if the intake anti-ice system was selected on after icing was encountered – ice already on the intake, and thus the heat acted as a deicer. This caused large lumps of ice broke away, some entering and damaging the engine; the damage being restricted to airborne occurrences.
Alternatively, the intake icing system could be overcome by the conditions – severe icing, or severe for the relatively low heat at low engine rpm, or due to icing system weakness/failure; blocked/leaking system, sticky valves – seen them all.
Thinking out of the box; any chance of sucking up ice/frozen snow lumps during the engine runups with low slung engines.