Found a white concrete wall that is not climbable on Livonia, it appears to be slightly smaller than the general grey concrete walls you see around Chernarus & Livonia. Unsure if this is a gameplay decision but it does feel like the player character would easily be able to jump over the wall or even climb on top of it because of the available space on top of it.

I was running from infected and tried to climb up onto the wall to get as much high ground space between me and the infected but I could not do it so I resulted in climbing on top of a bin.