Funny, I was thinking about this only the other day, when I heard ATC use "day-see-mal" for the first time (not that he used it for the first time - I heard it for the first time).
Being a very low-hours PPL, and the skies of East Anglia not being massively crowded, I've obviously not got a lot of RT under my belt as yet, but I have to say that virtually all the RT I've heard to date has been in plain English, other than "fife" and "niner".