Natural gas powered cars...

I would rather see larger federal incentives on realistic natural gas vehicles instead of limited range electric vehicles. Natural gas would be a larger economic benefit with jobs and tax revenue versus battery powered cars.
it would be a great transition fuel.

I wonder if cng vehicles could run on propane since you can get propane every where.

I think we should have incentives on both and hydrogen fuel cell vehicles. An unlimited range PHEV could be powered by electricity and gasoline, diesel, CNG, LPG, or hydrogen.

I believe a dual fuel CNG/LPG vehicle could work, but it probably wouldn't make sense due to the limited LPG fueling infrastructure and safety issues. Dual fuel CNG/gasoline makes more sense if you don't mind the price and space premiums.

Is there a way to refuel a CNG vehicle from a residential natural gas line?

Is that what you mean as home refueling appliances???

Yeah, the reliable refueling appliances are very expensive.

CNG Chat has more info on vehicles, conversions, and fuel.

Honda has partnered with a company that offers a home refilling unit. Severum mentioned that it costs between 9 and 16 thousand dollars.

The system is made by
phill which was partially owned by Honda. Phill filed for bankruptcy in 2010 and was bought out by another company. I found prices ranging from 2 to 6 thousand looking around online.

That premium includes the $10,000 (-$4,000 rebate) vehicle premium as well. The refueling appliances cost around $3,000 to $10,000 depending on quality, see CNG Chat's refueling forum for first hand experiences. A station based model makes a lot more sense to me, but I'm slightly biased.