When I spent my seasons out in the alps, 'punters' would regularly complain about icy slopes and icy patches. However they were mistaken about 98% of the time, and were actually moaning about very hard pack that is difficult to get an edge on.
Best to ski over such patches (and those rare icy ones)and turn on the softer stuff the other side.
The largest patch of genuine ice I've seen in the mountains was in
Flaine in January where there was clear a leak in some pipework and water was freezing across the slope - that you could have put in your G&T!
Our village was also an ice rink over christmas!