Hi Jim Jam,
ATG has not only an application server but also many other enterprise solution. You might want to take a quick look at the solutions provided by ATG on its website.
I guess
Work on java/J2EE which will use ATG and Weblogic.
should be
Work on java/J2EE which will use ATG or Weblogic.
If not, they might be using two app servers at the same time and transferring the requests to an appropriate server during the processing. I might suggest you to shoot an email to the company about it.
If I am in your shoes, I will just assume that it is an 'or'.
Co-author of SCMAD Exam Guide, Author of JMADPlus
SCJP1.2, CCNA, SCWCD1.4, SCBCD1.3, SCMAD1.0, SCJA1.0, SCJP6.0