The answer (at least in my experience this weekend) is yes!

Every time we go to a party, Emma and I have to take along our own cupcakes.  It is sort of a pain to make a batch of cupcakes and frosting every time a party rolls around, so I usually keep a stash of cupcakes in the freezer.  The last time I had frosting leftover (made with both non-hydrogenated margarine and non-hydrogenated shortening), I decided to try an experiment and stick it in the freezer rather than waste it.  To my surprise, it defrosted okay, albeit a little more liquified than before.  When I took it out of the freezer, I let it defrost and come to room temperature on the counter.  Texture and taste were fine.  Who knew?!