The Enemy-Territory engine is a modified Quake3 engine with enhanced features. I once checked out the wild west ET mod, and just by renaming the bsp file, I was able to load their modified, unfinished version of br_elpaso. Anyway, the map didn't render properly (I think foremost, because it used textures and shaders of ET which were neither included in the map package nor in SG).
Hm, yes, I converted the map from BSP47 to BSP46 using the bsp-sekai
tool by ZTM and I was able to load it on Smokin'Guns. Many textures was not rendered fine due to unknown shader keywords and I experienced some temporary freezes sometime while moving (but no crash), but perhaps it's due to the shader stuff, don't know. The map looks tiny but in fact there is a very large hidden trickjump level underneath the map :p. So perhaps the renderer tries mistakenly to render invisible things…
With translated shaders and recompiled map it should work.
I wrote a message on the map topic
at Splash Damage Wolf:ET forum asking for map source and license. I hope the author will be ok.
About the wildwest RTCW mod, I did not know it, it looks good, what happened to that project? Also, the wildwest map and this ET map are multiplayer maps with objective: not only rob the bank or classic death match, for example in this western ET map you must steal a dynamite and a detonator to be able to destroy the prison wall to free someone, it could be good to get that in smokinguns ! I loaded those wildwest maps on the Daemon engine
to have a look and I was amazed by some maps [note: unless some unknown shaders issues, all the textures seems there]. For example I've seen a kind of canyon map that looks very impressive but it's too large to fit the deathmatch or rob-the-bank gameplay.