I believe any lens benefits from IBIS. The lens is projecting a circle of light (image circle) that is big enough to cover the whole sensor. Some lenses it is just barely big enough, others it extends farther (a good conceptual go-by is lenses that vignette don't have a very large image circle, and those that are full brightness to the corners probably have a larger image circle).
So the larger the circle, the more you can wiggle the sensor around and stay within it, and there fore the more stops of IS you get. I'm sure someone could go dig through patents and figure out which lenses have what size image circles and make predictions on which end of the spectrum of IBIS stops they will get. But that guy won't be me.
A lens with IS has to be able to communicate with the IBIS system, in order to make sure the moves they make are complimentary. This communication may not be as sophisticated between EF lenses and R bodies as it is between RF lenses and R bodies, i'm guessing simply on account of this feature wasn't available in EF and the R system might have some stuff specifically programmed for it. But it works and adds something to all lenses.
-Brian