Sword ferns are evergreen but not really - last year's foliage can look good for another year or not that long. Since yours was newly planted I would say its not going to be a year. Your indication is, do you have new fronds yet? They should be out or coming out by now. Or at least you should be able to see them tucked in the center and healthy light golden brown, not dark brown or mushy. If you've got new stuff coming out, cut last years foliage off. The new foliage will be much hardier as the plant gets used to its location.

Sword ferns are evergreen, but for best appearance, cut off last year's foliage in spring, some even do it in late winter. That said, your description doesn't sound like old foliage, it sounds like dead foliage. You CAN leave on the old foliage and it should still remain green, but will eventually (several years) wither and fall off on it's own. But if it's completely brown and dried up, it's no longer alive. This is pretty rare, sword ferns in my experience can get by with very little supplemental water. I have even transplanted in the middle of summer and just watered in once, and they got by fine without turning brown. But if they have NO water, I have seen them dried up as you describe. Since yours made it through the summer and fall and then browned in the winter, I'm at a loss. It can't be water problems, and I have not known them to be disease prone. I would just cut off all the dead foliage and hope for the best. You really should have seen new growth by now though. The new fronds on mine are about as tall now as the previous years growth I cut off a couple weeks ago, although they have not yet fully flattened out and assumed their normal horizontal spread.

Aaron