This group of hams into HSMM mesh networking in the pacific northwest region of the USA has made HSMM-Mesh on Ubiquiti devices happen.
It's not a pre-rolled firmware build yet. But rather a step by step how-to on how to roll your own:
Configuring OpenWRT Devices for Operation on the NW-MESH Network via the GUI:
http://www.qsl.net/kb9mwr/projects/wireless/NW-MESH_GUI_Config-2012101401.pdf
You start by flashing OpenWRT, and then add in the OLSR module.
OpenWRT is very powerful.
This is ideal for those seeking a customized mesh network. Idea for those seeking to use Amprnet IP addresses (44/8, 44net) rather than the 10/8 network that is pre-configured in the BBHN builds. This eliminates the need to setup GRE tunneling as 44net is already connected.
In this screen I am showing the add software tab, where you can add OLSRD
This screen show the available wireless channel bandwidth options. Sadly 10 and 5 MHz/ half and quarter rates are not available without some editing of config files.
(Note: The software says it's on a lower channel, but when you go to confirm this with a spectrum view, there is nothing there. Turns out the underlying kernel module, ath9k has to be modified, this fellow ham has documented how: http://yo3iiu.ro/blog/?p=1301)
Available transmit power options.
This shows how to select the country code of 00 for world.
This is the status page showing -1 as 2402 MHz.