I really like the Plastuct (and Evergreen too) products. O scale is listed as 1/48 on their website so a little over-sized for 28mm figures. However, in cases like this where it is just scatter terrain it isn't that noticable. Had I slightly smaller trusses I would have chosen them over these. As they got left behind and have suffered through a couple of rainy seasons, the rust has set right in.
The lumber was dead simple: cut 1/4 balsa; scribe grain with sculpting tool; glue together; prime and paint.
I still have two more pieces coming in the post; once on they are on the table it may be crowded enough and there will be no need for more shrubs.