There's a woman here that has a set up like this only it is inside a van, she is a mobile dogwash. We used her once, N didn't 'speak' to us for about a fortnight
This is something that went round the grooming forums a few years ago now. I can't imagine HOW it's meant to do a good job...I'm not sure I'd want to take on grooming a dog after it's been in one of those contraptions. :-/