As yet, no evidence has surfaced that any pipeline company withheld gas supplies and diverted them to spot markets to take advantage of the huge price swings

See Are pipeline companies too powerful? Texas' unusual gas market faces fight over winter storm costs by James Osborne of The Houston Chronicle. Excerpts:

"James Mann, general counsel for the Texas Pipeline Association, said the market, not pipeline operators, sets prices. The power companies that got “burned” in the blackout opted to rely on spot markets, rather than pay a premium for futures contracts that guarantee a price at a later date, he said. These contracts, known as hedges, protect buyers against future spikes in prices.

“The market price is set by bids and offers, and if the price went up to $400 it’s because people were offering to buy it at that price all over the state,” he said. “People get to choose whether they’re going to have secure supply or get cheap gas, and have to worry for three or four days every few years.”"

"Asked about charges that Energy Transfer and other pipeline companies are abusing their power, Mann, the attorney for the Texas Pipeline Association, was incredulous. He said he has heard the complaints for years, but no one has produced evidence of companies’ withholding space on their pipelines to drive up prices.

Eric Fell, a power market analyst at the energy consultancy Wood Mackenzie, agreed. He said the Texas system has problems, but prices on the federally regulated interstate system also spiked during the storm. On certain interstate pipelines in Oklahoma, he said, prices soared higher than at the Houston Ship Channel.

“Yes, the people on the right side of this got windfall gains,” he said. “But the idea (power companies) got gouged is sour grapes. They got screwed by Mother Nature.”

If gas prices went just as high on the interstate system, that would suggest, as pipeline companies argue, that it was the “free market” that drove up gas prices during the storm, not the companies themselves."