The 2nd Edition of UEB (2013), page 32, shows 3 symbols for the natural, sharp, and flat signs. These are all two-cell signs, curiously starting with (3456), then the Braille Music Code accidentals. The rule (3.18.1) says: "Follow print for the transcription of the natural, flat and sharp signs within UEB text."
The examples in UEB show these two-cell signs following names of notes, in chord symbols, and in chord progressions, as well as "standing alone," all in narrative context.
Will transcribers need to use these two-cell accidental symbols in the narrative portions of music theory and other texts about music, when UEB becomes effective in 2016?
Yes, when in literary context, the narrative parts of texts, the two-cell UEB symbols should be used instead of writing out "sharp" or "flat" as we have done in the past. If a chord symbol or chord progression is being used as an entity, it should be prefaced by the music prefix and the single-cell sign from the music code employed. There will be cases, like the third example in Section 3.18.1 of UEB, when the transcriber will have to decide whether the item in question is music notation or is continuous literary material. Either will be correct; the transcriber should be consistent within a given transcription.