IMPORTANT EDIT: Determinate or indeterminate: A hard frost murders all tomatoes. Bring them inside for the night if thats a risk.
Edit: Lo siento, mi espanol muy malo, pero: Alguno tomato no muerte, alguno muerte. Es possible sus plantas no produca comida durante navidad pero mas fuerte en verano. Ten mucho cuidado durante un noche con nieve o otro.
First, there are two types of tomatoes: determinate and indeterminate. The words mean exactly what you'd think in terms of life cycle. A determinate plant will grow, flower, produce fruit, then die. An indeterminate plant will keep living and keep flowering, although they sometimes need "cues" to flower.
If you're plants are still alive my guess is they're indeterminate, or a hybrid. They may not produce fruit over the winter but you'll have a head start in the spring! You may need to pay extra attention to fertilizing though as they may have used up all the good stuff in that soil.
Also, check out some youtubes on tomato pruning. There are branches that don't make fruit, and especially with an indeterminate, you can increase the yield by having a long living plant that you've pruned into mostly fruit baring branches over the years!