I am not your zone but your garage sounds close to my north fern garden under the eaves of the house. I don't cut my ferns back but they see little light during the winter. It's on the dry side so I would worry about your ferns sitting in cold wet soil. Can you guess the temperature of your garage on the coldest nights and see if your ferns are hardy to those temperatures. I would go easy on the water and check them once a month. Some people seem to be on the cup of water a month program. My guess is that your chances of bring them through are very good. pw

There is a little heat in there from a vent in the wall -- I'm sure it was put there to keep the main water shutoff from freezing. I keep a lot of my canned goods in there and it never freezes. Have also overwintered a large pot of Tropicanna cannas for several years, and some pots of hosta before I knew (thanks to this forum) they could be stacked on their sides on the north side of house.
Sunny

We just get frosts no hard freezes but the fern bed is under the eaves of our unheated sunroom that never sees the sun. I don't recall any of my fern names except 'Painted Japanese " fern but I have half a dozen kinds. Your ferns should do well in your garage. I buy them to put in pots with impatiens and begonias. The flowers go to sleep and the fern takes over the pot by spring. A big hanging fern is a beautiful image. pw

I call them Boston Ferns but they aren't from Boston. I didn't know the answer to your question, so I looked on-line. It seems they are messy in winter when people bring them in and shed their leaves. If you are already storing plants in the garage try it. They might do better in a cool place than in the house. Cutting them back might be good to avoid a mess.