We (dba team) do run the Solaris boxes where the DB are intalled, we combine syadmin + dba , so no conflict. For the linux boxes is a different story, but we have sudo so.... :)
The severs are dedicated to run oracle exclusively, so it is better if nobody else but the DBA team does touch the machines. The sysadmin team only install the linux part and some initial configuration, after that they hand the server over to us...
I think we are lucky...
-- Nilo Segura Oracle Support - IT/DES CERN - Geneva Switzerland