I think Madden 07 is the same as 08.
Decompress the uniforms.dat file using stingray's decompressing utility. viewtopic.php?f=13&t=21906#p131010
Then with a db editor load the roster, go to the team table and get the europe team's TGID values. Then go to the TUNI table and write every team's TGID UFID values. The UFID will be the location of the uniform in the uniforms.dat file.
Using the Dat File Replacer (DFR4/5) load the uniforms.dat file. Check on zero based, select the location, load your XFL uniform, click on replace and save the uniforms.dat file.
If you have any more questions well be glad to help you.