Here are the maps that I have successfully converted.

NB! This version of VQ4DM7CTF (map-vq4dm7ctf-.pk3) requires textures from map-vq4dm7lite.pk3, too, because of limitation at this site (files must be smaller than 8 MB).

Manual how to converts maps from Q4 and D3.

Instruments:

1. QuArK 6.6.0 Beta 6 from here http://quark.sourceforge.net/
2. GTKRadiant 1.6.3 (not 1.6.4, as its Surface Inspector works incorrectly) or a good old Q3Radiant 2.0.2
3. Q3MAP2 (q3map2_fs_20g or 2.5.17)
4. BSPC (2.1i)
5. Paint.NET

Algorithm:
1. Extract all files from all the *.pk4 files in <DOOM3>\base or <QUAKE4>\q4base
2. Open <yourmap>.map in QuArK and save it as 'QuArK map (*.qkm)' and further as 'Structured text for hand-editing (*.qkm)
3. Close the map in QuArK and open it in Notepad (or WordPad) and replace Game = "Quake 4" by Game = "Quake 3"
4. Re-open the map in QuArK (now it will be Quake3 game mode) and save it as 'Quake .map file (*.map)' into your work folder, for example, <QUAKE3>\baseq3\maps
5. Open the map with in Notepad (or WordPad) and remove all 'textures/' as Q3 uses short path for textures names (NB! as Q4 has folder 'textures/mptextures/' you should replace '/mptextures/' by '/mp/' previously and rename the folder 'textures/mptextures/' to 'textures/mp/' )
6. Compile the map with Q3MAP2 (with -bsp key only). It's just a raw compilation to get list of necessary textures (and shaders)
7. Search necessary shaders through <DOOM3>\base\materials or <QUAKE4>\q4base\materials to define layers to make necessary textures
8. To make new textures see my manual at http://www.quake3world.com/forum/viewtopic.php?f=10&t=51222&sid=eb4d32bd1efa3000552b0f533703e697
9. Write shaders for complex textures and place it into <QUAKE3>\baseq3\scripts and insert the name of your *shader file into shaderlist.txt
10. Open the map in GTKRadiant (NB! change default project settings to work with brush primitives) and edit it as you wish
11. Compile the map with Q3MAP2 (to make *.bsp) and BSPC (to make *.aas - for bots)