I have checked a number of CD's which I have to hand (But no inserts)
Several, but not all, have MCPS on the CD itself, including Steeleye Span (Spanning the years) and Boys of the Lough (West of Ireland)

But the font and style vary, and I think the letters MCPS are sufficient. Of course, that is only for the UK; I think there are equivalents in other countries.

I take Dick's point about CD-R, but it should still have the MCPS if they have been paid. As I said above, we use CDR ourselves, and put MCPS on the insert. And I am sure that some of the Bulmerised albums would have substantial sales, because they include many of the best folk albums from the UK revival (see full list in a different thread).

Bright Phoebus was perhaps not a good example, because there might have been no third-party rights.