It's the same stuff. Several models are already available, including the Honda Civic and all of the full size trucks, I think. And home filling stations are available too. If you want to go that route, go get it, you can do it right now, you don't have to wait for anybody.
Though in vehicles, it's very highly compressed, not exactly like the line in your house. The home filling stations I know of aren't compressors, they are storage tanks with car hook ups. You have to call someone to come fill it, who comes in truck like a propane truck. And it can take hours to fill your home storage tank. Once compressed, though, it is very quick to fill your car from that tank.
I don't know if you could get a compressor like that to take it directly from your gas line, or if you'd have to wade a mountain of government regulation to do something like that, considering the dangers of compressing natural gas from a line that is connected to everybody else's house. Compressor breaks and everyone gets a BIG spike in pressure, hehe. As it is, only about 50% of homes have gas lines anyway, so it's never been seen as a mass solution.
As far as cars themselves, the gas tanks can't be shaped like a gasoline tank, and in order to get respectable range, have to be huge. In a civic, for instance, you lose pretty much your whole trunk, and still get a range of only about 200 miles.