Strangely enough I have added orange juice in the secondary; a 1/2 gallon to be precise. Did this in a "Beer Captured" recipe for Fantom. Do a search on HBT for a Fantom thread where I posted the recipe. The base was a beer containing some small % of wheat malt, 1 lb or so.
It worked out quite well a good beer, but without ever having Fantom I have no idea how close it came to the original. Remember to add pectic enzyme so that the beer will clear.