So, it seems it's not commonly known but Buggy Heat in both Japan and Europe included online connectivity. The US version, TNN Motorsports Hardcore Heat, was a completely offline title. While the US version is said to have refined the controls, it is by far the version with the fewest features.
The PAL edition of Buggy Heat adds the Internet mode, which allows you to connect to the Buggy Heat website. The site is currently down and I've not yet attempted to access this site on the Wayback Machine so it may or may not still exist in some form.
However the Japanese version not only included the online website mode, but DLC in the form of an exclusive in-game option of AI Data. In short, you can create an AI racer and had to train it up to compete. This data was also used for online and offline tournaments, the latter of which occurred at CRI's headquarters in Japan.
This was all learnt from the website, which I am currently in the process of restoring (I finished and sent Xiden the MSR site work, it just needs databases added) and there are several interesting features.
However my main question comes from the site's FAQ section, the only FAQ page missing (FAQ 11, ans11.htm) which is as follows;
11. About the Capture Book
11-1. Do you have a Capture Book?
I've never heard of the Capture Book before, it's not mentioned anywhere else on the site and a quick Google search turns up nothing. Does anyone have any idea what it is? I'd love to learn a bit more about it, if possible.