BNSF has zero interest in upgrading the track to handle higher speeds. That would not help operating ratio even if it let them move more freight and charge higher rents. For US railroads operating ratio is God.
The funny part is high-speed passenger service is usually very profitable. The trips are so short you don't need to turnover or time out crews. A lot of routes you don't even need to put them up in a hotel, they go out and come back. That keeps labor costs very low.
For the curious I once ran the numbers on China high-speed rail vs California's HSR project in terms of miles of HS track. A rough estimate was about 3x the cost to do the project here in the US. Given wages and most importantly property values in California that actually isn't out of line. China has the same vast distances across low density areas as the USA does so you can't blame it on Europe and Japan being higher density. Because they cover large distances on some routes they pay (all else equal) more than others do. China has simply invested more in their rail infrastructure because they see it as a priority.
FWIW The USA used to do those kinds of investments. It was government-backstops of investments that allowed the Transcontinental Railroad project to happen in the first place. Plus railroad land grants (free land if you build a railroad).