Triple axle BushTracker

Dear forum,

Since the 'search' option didn't reveal any relevant posting (nor did any previous Googling in general), I probably didn't use the right keyword (most importantly a model name), but after seeing the triple axle BushTracker on this and the BT-site itself (and finding not any info there either), I was wondering what the design of its suspension might look like.
I *could* imagine some kind of double/linked tandem, but even without knowing the exact design of the ordinary BT-tandem, that would become rather complex I guess.
But since BT is so proud of their tandem design, I also doubt they just added a solitary axle to a tandem, without any linkage.

Willem (no need to convince me on the bogie-tandem concept itself, I even bought a Volvo C306 6x6 firefighter for that very reason....;)) Jan
(just wondering if one could add a 4th, driven axle, to that configuration too....:))
(a PTO-driven trailer (driven by a second diff-side PTO) has already crossed my mind, but a linked 4th axle on the vehicle itself sounds more fun & challenging....:))

Greetings from Holland....:))