It's a great idea for the City of Hoboken (Copenhagen does something similar with bicycles). 42 cars might not be enough, but it is a good start. I've often wished for some type of alternative transportation from the west side of Hillsdale, especially since I work at home and use my car only for errands a couple times a week. That said, not sure how well this would do in less dense parts of the county. This does make me think of all the real estate dedicated to parking lots and expensive cars, maintenance, insurance, etc. just for short trips to stores and the train station.
Portland OR has been doing the bicycle thing for quite awhile too. In the larger cities it is a lot easier to get to the shared bikes and cars. Yes -Wish there were more carpooling in this area. Schedules are difficult to synchronize.