Pawns can meditate on cube sculptures to gain psyfocus. However, very anecdotal evidence suggests some odd interactions:
Cube sculptures will have their Meditation Focus Strength enhanced by nearby regular sculptures of sufficient quality.
Regular sculptures will NOT have their Meditation Focus Strength enhanced by nearby cube sculptures (tested with Good quality CS).
I will investigate when I have the opportunity if cube sculptures are enhanced by nearby cube sculptures, but my guess is no. Most likely, CSs are tagged as valid foci, but are not on any 'can enhance focus MFS' list.