the "3 bass tracks thing" isn't about duplicating a DI, it's about capturing the same performance in 3 different ways. IIRC from the jens bogren thread, TGCD bass was like one mic right in front of the 810 ampeg cab (probably a neumann, can't remember), another one a few feet away (on a chair, apparently. i think this was a shure of some sort), and the DI.
he said he did a hard pan on the two mics, and use the DI with very little lowend but some distortion in the middle. important to check in mono to avoid phase issues obviously.
edit: and no, bass wasn't double tracked all the time, just for some of the more mellow, bass driven parts.