Wiki's Blackberry Tour article says the browser supports HTML, and doesn't specify anything further. I would suspect the mobile site uses something more sophisticated, in some way.
I really don't know anything about code, other than theres some PHP/SMF stuff going on here, which I believe is an overlay built upon HTML, to make it extra fancy. So, we can use HTML to write the image tags, and so forth, but when it comes to the dynamic buttons for navigation, there may be some code involved in the design of the buttons that your phone is unable to read or interact with.
Thats just completely winging it, and I'm sure to be half-wrong, at the bare minimum. But you deserve an answer, so until a better geek pipes up with actual knowledge, that'll have to serve as a basic answer.
What I can say is, theres probably no fix forthcoming. Like, I doubt theres any simple check-box one of the guys can enable to resolve your incompatibility. Although, Blackberry may solve it, if they release a push. But I also doubt the likelihood of that, because they're working on newer phone and tablet technology, with hotter processors and all that jazz. (again, conversational speculation)
Anyway, hope that helps.