Hi, Ed. It's been a long time.
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.
Good to hear from you!