This guy allready done converting most of the maps from ql to q3,+you can even find some of cs covertions as well: http://rutracker.org/forum/viewtopic.php?t=3884121
While all those maps are listed under cpma section they are fully playable in vq3/osp as well. (You need to register there first in order being able to dl that torrent file)
Edit: I see his website is under construction or something like that...
he also made iron works, siberia, quarantine, trinity... worked on rage and is nowadays at infinity ward contributing to cod ghosts.
Note that I only approve the usage of the bsp files.. the QL stock textures are property of id software, I generally don't approve of using them but I wont come to your house and murder you because it is not my business. :)
the map uses quake live textures which don't belong to the map, but to the game. if you use them in q3 as well, it's basically illegal unless id allowed you to do it. but he don't care cuz he's a mapper and he don't want to know what you do in your free time.
And despite of QL being better, Q3 is basically how QL started considering it's very very similar. And there is lots of CPMA players here too that may want to use the maps.