Lou, do you have any idea how expensive gas will have to get before it starts paying to take manure-digester gas and landfill gas and clean it to pipeline quality?  Those are sources that aren't likely to have the sliding production and would tend to change the decline curve.
I am looking for conformation but was told Midamerica energy is doing this now in the midwest, particularly Iowa.
Engineer, your question is about direct substitution in NG supply, but in general could there be a sea-change associated with present NG prices with more consequence for infrastructure than $70/barrel oil?

At $14 per million BTU, and 3412 BTU/kWh, even a (generous) 70% efficient peaking plant implies 6.8 cents/kWh. Shouldn't that be enough to tip many scales toward growth in reliance on wind, for example, with or without subsidies, with or without successful green marketing, with or without top-level political will?

Try 35-40% efficiency for a simple-cycle peaking plant, 55-60% for a combined-cycle plant (which I understand cannot be throttled fast enough for peaking).  You're looking at a minimum fuel cost in the 8¢ range for combined cycle, 12¢ to 13.6¢ for simple-cycle.

Yes, I expect wind to be driven very strongly over the next few years where generation previously relied on gas (though solar follows the A/C load peaks a lot better).  If coal winds up in demand for Fischer-Tropsch synthesis of motor fuel and it becomes hard to increase production, wind will wind up being valued where generation is coal-fired too.

It may still be a good idea to have production credits for the next few years (perhaps 5).  It pays to think of the future even if utility accounting rules won't let them, and a tax credit is probably easier than un-screwing the screwy system in time for next year.  When conditions suddenly switch over to wind, solar or cogeneration being a REALLY good idea due to whatever event, I'd much rather that installation had begun 5 years before than 18 months after the crisis.

My mistake.  Alliant Energy not Midamerica has methane capture up and running commercially. http://www.alliantenergy.com/stellent/groups/public/documents/pub/012042.pdf

A quick search shows that the midwestern electric and energy companies are investing heavily in alternative sources.  Very large windfarms, ethanol, biodiesel and methane are on line in Il, IA, MN, SD, and Ne.

For those interested, Midamerica is owned by Warren Buffet's Berkshire Hathaway. http://www.mindfully.org/Energy/2005/Buffet-Berkshire-PacifiCorp24may05.htm

Berkshire has been buying lots of electric/energy companies recently and investing in alternatives.

That Alliant PDF claims bio-methane to electricity, not to the pipeline.  If the local generation is coal-fired the net cost reduction is quite a bit less than would otherwise be possible.
Alliant is the natural gas distributer in central Iowa as well as electricity.  I believe they control at least one main pipeline so they can feed their electric generating plants.  Alliant and Midamerica have built NG electric generating plants recently because they come on line faster than coal and have a tax advantage due to lower total emissions.  You have a valid point per onsite production if that is the case.  I was told and am trying to confirm that Alliant has a methane pressurizing station feeding a main east-west pipeline.