In my last lot we could fly NDB and VOR overlay approaches to the minima on the chart, treating it as a DA, if we flew a CDFA, which in fact was mandated anyway.
That minima in most cases was the 'old' MDA and in a few cases was the 'old' MDA plus a bit but I guess the new minima was derived differently.
I can't give you a reference for it (wouldn't know where to look and can't be bothered) although it was, without doubt, written in the Ops manual and, therefore, approved by the authorities.