A few years a go I had a PekinXrouenXrunner cross hatch eggs in winter.
Now I have been told they cant breed in winter? So was it just a "freak thing"?
I have fertile eggs and hatch year round - so yes they do breed all year round. The issue of going broody and hatching is all together different though. Ducks are less likely to go broody until the first signs of spring- and when sitting in the middle of winter- the freezing temperatures can greatly effect how many embryos survive to hatch.
So no- its not exactly a freak thing- but something that doesnt happen too frequently.