It can work on both. The trucking example you cite is one that's currently being used in Nova Scotia, where you have an existing franchise, a small franchise, like New Brunswick's, a relatively young natural gas distribution industry. That franchise has some small communities that are quite far removed from the main pipeline. That pipeline can't be extended affordably, so the substitution strategy is to move natural gas as compressed natural gas from one point to another and into a distribution system.
So it is possible to do that, and there are precedents for it in the Maritimes.