There are a lot of dirt roads near me, and I'm sure the suspension helps a lot on them, though I do tend to avoid them. But on a recent ride, it was either take the relatively flat dirt road or take a rather steep set of hills on the main road.
It's a bit hard to take pictures of the brackets, they're incorporated into the bike and I'd have to do some disassembly, and they're black. I don't have any design files, I'm just a CruzBike customer.
The basic idea is simple, it's got two bends so that the 135mm wheel axle/cassette fits in one set of holes and the bends go around the cassette so that the 100mm wide fork can be mounted in a hole. [got it reversed earlier] And there's another set of holes for the front triangle. I suspect getting the shape and arrangement and placement of holes/slots right was a lot of trial and error for John Tolhurst.
[update]
Ok, here's
John Tolhurst's patent application for the CruzBike Conversion Kit, which shows details on the brackets, especially figure 6.
I don't think I have anything more to add about the brackets as I've already given you pretty much all the information on them I have.