Yes, I used a ShiftMate for a Campy Brifter with Shimano 9 speed RD and Shimano 9 speed cassette. Worked perfectly... and better than when I had all Shimano (Shimano Ultegra Brifter quit working & Campy Centaur 9 speed was available).
a great bit of kit, I have one on my road bike, I run Campag chorus 10sp shifters on 9 sp casettes, also run 9sp shimano wheels.
I have a set of 9sp Veloce levers too, but find the chorus with shiftmate is a much smother change.