I am going to use UnrealTournament maps (*.unr) in my engine, but I cant find any information on .unr file format. Can anyone help ?

the unreal map file is under license I heard..
You have to buy the license to load them! It is better to load Quake2 /3 maps files =)

CYA

This link should help clear up the contents / requirements for using .unr packages.
http://unreal.epicgames.com/Packages.htm

"Licensees may use all our .u packages except UnrealI verbatim or you may modify them to fit your needs. Bear in mind that it is attractive to use them in an unmodified form, as that makes merging with future code updates much easier and makes it easy to isolate problems in each others'' code.

Licensees may use the UnrealI package as a reference and for internal development use, but the content in UnrealI is specific to our particular game, and it mustn''t be used in your final product.

Licensees should create one more more new packages, for example "WheelOfTime" for their game-specific content. Keep in mind that your package and UnrealI can exist side-by-side during your development cycle until you''ve fully migrated away from the UnrealI specific content."