I don't know what you mean by "politically sensitive"

The CPS does not track what happens to prosecutions it has taken control of. Conveniently they're just CPS cases once that happens, and so the question "What happened to them?" is magically a manual discernment and not amenable to FOIA.

We can ask, and so we have, how many they took control of. The answer is typically in the range of few dozen but not a hundred per year. Since these then disappear into their normal case system they could be prosecuted exactly like any other CPS case, they could be dismissed immediately as erroneous, or any of the usual dispositions for a criminal case, and the CPS won't tell us (if we're to believe them, it doesn't know)

We know a lot of private prosecutions are by the RSPCA, since they have funding to prosecute animal abuse and money is always tight. But presumably in the typical case the CPS is either never told or if it is explicitly told by either party it chooses to do nothing and allow the prosecution to happen. So those cases would not be on the list where the CPS took control.