The startup equipment cost for a MT plus heat exchanger is about $70K. Install is another $20K. Maintenance is at least $40k over a five year period of time. Cost of Nat Gas will swing with Nymex unless you've locked in annually. So, the initial capex is $90K. Annual maint is $8K, cost of operations is cost of nat. gas...assume $6-7 for a decatherm.
What does all that get you? 60kW. Not enough to do more that take off the top of a peak for many customers. Sure, piggyback them together and get up to 1 MW or so. IT is, at this time, cost prohibitive in the large majority of the country. It's a great concept but financially, it doesn't work.
What we have continued to do is measure the initial capex against reasonable risk assumptions for a negative business impact and associated losses from a blackout.
In the case of the NYC blackout, even those with gensets and MT's experienced problems because of fuel delivery. Diesel and nat gas is pumped with electricity and most of the fueling stations have no backup power.
It must work for some folks, or they wouldn't be selling.