When I worked for a company that had a gas plant in the northeast, it was permitted to run for 4 days a year on oil. For several years, they never did it but did run a test once to make sure it worked. There were several oil tanks on site to store all that oil and there were oil tankers there for days afterwards filling up those tanks after the test was run. So the gas plants in texas could have been set up to run on oil. They probably just never figured they'd need it and didn't want to spend the money on it. Gas curtailments mainly happened in the winter and I guess maybe the oil was there in case there were issues in the summer. The plant made a lot more money in the summer than the winter. I think most gas plants out there are combined cycle so they already have heat recovery steam generators. Basically I believe at one point you could get more money for running a combined cycle power plant than a regular gas one if at least 5% of the steam energy was used.