I saw that on CL too, and it looked amazing. My vet and I were actually talking last year about doing something similar, but just don't have the wherewithal to pull it off unaided. The trip logs made it look like a wonderful experience.
My problem with it is that I've looked and looked for other references to them on the web, and can't find any. They say they've been doing this for several years, so you would think more info would be available.
Also, you have to purchase a $40 "membership" before you can even be considered for a position on one of the trips.
They are listed as a 501(c)3, so I suppose they are probably legit, but it kinda raised some red flags.
Plus, they are spamming the snot out of Craigslist, and don't really appear anywhere else. It just seemed...iffy.