Both of the new Texans with the TX2 upgrade I've seen this month had Carbon Fiber bottles. Honestly, I've never seen a steel Texan bottle. The origional metal bottles are ALUMINUM and only rated to 3000 PSI.
I have two of the aluminum bottles on my parts shelf that came off Texans when I switched to CF bottles long before AirForce did. They don't even make good pony bottles for refilling in the field since they only go to 3k and will not fill a rifle to full pressure.