Okay, I had a play with this this morning. A couple of things to note:
1) The individual trees and shrubs can be brought over just fine. I'm not sure if they look any better than Speedtrees but the one big advantage they have is you can change the materials on them (which you can not do with Speedtrees). Here's a scene in iClone where I took the maple tree they provided (with green leaves) and replaced the leaves with my own coloring. Now, to be fair, Speedtrees comes with enough variance (like fall foliage) to cover most circumstances, but if you need, say, alien stuff or very unusual coloration you're out of luck with Speedtrees. OTOH, they have no physics (unlike Speedtrees) so you won't get the wonderful look of the branches blowing in the wind (you might try applying some spring stuff to them, but it's above my pay grade).
2) No way are you going to use the Ultrascenery system to create the kind of landscape they show in the images. Oh, you *can* create such things inside of iClone, and they aren't any different than any other items there (so can be exported) but they take a TON of resources and time. On my machine (which most likely is much better than yours) it took almost 15 minutes just to generate the default NW forest in Daz. And this was nearly ALL instances (if you aren't familiar, instances inside of Daz don't get exported, so you only get one copy of each tree, for example. The default NW forest 1 used 500 copies of around 100 trees). Now, you *can* convert instances into Objects (I have a Daz script which does this and which I use on occasion) but you couldn't even load in such a scene in Daz, let alone export it and use it in iClone.
Even with all the instances it takes freakin' forever to export. I gave up after two hours of trying to export that default scene above. So I switched to a much sparser scene (only took 8 minutes to generate and around an hour to export) and... it didn't come into iClone as anything usable.
So the bottom line is this - if you want individual trees and don't mind not having wind FX then, sure, that pack is fine. Just don't expect that landscape they show. But, honestly, Speedtrees is SO much better (and you can use the new terrain generator script to do a much better job than this Ultrascenery thing can do).
Alienware Aurora R12, Win 10, i9-119000KF, 3.5GHz CPU, 128GB RAM, RTX 3090 (24GB), Samsung 960 Pro 4TB M-2 SSD, TB+ Disk space
Mike "ex-genius" Kelley