I am running into a lot of transcriptions where the EN dash is used between numbers and the EM dash mid-sentences. (Often times appearing very near to each other.) In the past, I have converted the EN dash to hyphens. However, the UEB seems to indicate the better way is to use the dash for the EN and the long dash for the EM. Is the latter the more correct way to handle these situations?
No, the long dash is *long and is rarely seen. Generally, the EN dash connects and the EM dash separates or disconnects. At least, that's how it's supposed to go. But the UEB principle is to follow print, which is often erroneous in its use of hyphens and dashes. So, then, continue as you have been doing. You only need to use the long dash when there are hyphens, dashes, and long dashes that all have different meanings.