If you use a Q3 bsp then placing lights in Irrlicht won't work. I mean, don't expect your bsp map to cast shadows from lights placed in Irrlicht.
The good thing from Q3 maps is to compile everything so that you get your light-shadowss "baked" onto textures, then you reinforce the map in Irrlicht with light billboards or particles and stuff. But the shadows of your map must be calculated by the bsp process.
If you want dynamic lights casting shadows and interacting with every object then you must model everything and they say the best model format is .x (although you can work with 3ds or obj or even ms3d - check the special fx tut for casting shadows stuff). Collision in Irrlicht is triangle based so it's not a problem if it's on a bsp or any other 3d format. In the end all that Irrlict sees is triangles. Agood (vey good) level editor that exports to .x is catography shop:
http://cartographyshop.thegamecreators.com/
the problem is that it's not free, but it's not too expensive either. It's also license free, so you can use your maps commercially with Irrlicht.
hope it helps. You get my point? Oh, one last thing. Dynamic lights only work in DX, opengl still isn't supported fully on this regard.
oh, I forgot, here's my test level. It would be a good reference for you. The whole map is a Q3 bsp with lightmaps, but the water, particles, alien model and circling light is placed in Irrlicht:
http://www.theshower.nl/cgi-bin/genesis ... is/AFC.zip
If you got problems running the test map, replace the exe with this windowed version:
http://www.theshower.nl/cgi-bin/genesis ... ndowed.zip
and here's another file I uploaded showing everything modeled in 3d formats (no bsp), and casting shadows. Source included-commented so it's gonna be of great help. It's a modded version of the special fx tut.
http://www.blackspork.com/files/display3d.zip
check this poll:
http://irrlicht.sourceforge.net/phpBB2/ ... 30&start=0
ok, enough chat....hope it helps
)