Heh, I wouldn't consider tf00t to be persona grata round here but at least his science stuff has always been solid

He's right, but he spends too much of the video focusing on the fact that the train is burning fossil fuels without acknowledging that the idea is that it's using fossil fuels that were going to be burned anyway until near the end. Once he does acknowledge that he rightly explains why it's not viable*, but that should have been near the beginning of the video, the first time regen braking was brought up, not the end.

* 1. the regen braking could just be used to help accelerate the train instead, thus requiring less fossil fuel total and 2. the weight of the whole CCS contraption probably ends up increasing the amount of fossil fuel burned by more than the amount reclaimed from regen braking.