I've got an engineering back ground, and lived in TX, and various coastal regions, those rigs bring back memories.
I think any equipment that has fuel flexability is a great thing. It keeps the market in check more quickly, as users can change from tank to tank instead of each time they buy a vehicle. I'm certainly going to keep my eye out for these, especially on the used market. I've been involved with a handful of alternative fuel companies, and our next venture will be along the same lines. Save to oil for plastics and lubrication, domestically we've got plenty of ways to fuel the countries transit needs, but the higher the cost, the longer the transition time.
Do you know if you have many public CNG stations near you?