According to the two TechNet articles below, a user with the ‘take ownership’ permission on a file or folder should be able to assign ownership to a group of which they’re a member. Unfortunately, it doesn’t seem to work that way.  An error is thrown indicating that the user should have ‘restore files and directories’ permission in order to assign ownership to a group.

http://technet.microsoft.com/en-us/library/cc753659.aspx
http://technet.microsoft.com/en-us/library/cc780020(WS.10).aspx

Thanks! to FK for raising the issue (which contradicts information in the NetVision paper on Windows Access Rights)  It’s a fairly obscure find, but worth understanding.