[TomGuy]

I don’t know if anybody has plans to ultimately build it as a ten-to-twelve-lane car-truck-separated monstrosity

I think the 10-12 lane reference is the width of the right-of-way. It would include the actual highway lanes, plus railway(s), utility and pipeline areas, access roadways, etc.

[TXnMA]

You have no idea what you are talking about. Here is the official layout:

Soure: http://www.governor.state.tx.us/priorities/transportation/images/transtexas.jpg