Ok because Mordsspass (and me too) asked how install the Serverside downloaded maps into your UTGame folder.
To do this follow this 3 steps :D
Step 1: Open UT3Tweaker and click on the Icon with a plus/crosshair.
Step 2: Open Cache Converter in the upper list.
Step 3: Now make the selection of the maps you need (I think its not good when you choose some who are already downloaded). After that press the Icon with the 2 crossing arrows, now wait some seconds and a message "Sucessfully installed" or something like that appears.
Now your done.