Its not quite the same thing but has anyone experience with the thing that teaches cats to use the human toilet? I think it starts off with a litter tray that fits into the toilet bowl so the cats get used to jumping up and going "on the loo", then you have a litter tray with a hole in the middle so the cats get used to the water in the toilet, then one with a bigger hole so the cat learns to balance over a hole with water - and then you remove that.
I have heard of cats using toilets and do think it is a good idea but I am not convinced the device to train them works and it is quite costly. It would be interesting if anyone has tried it and can give us first hand information.