What type of engineers......?

tony stark is most probably a mechatronic engineer. Cern would most probably hire physicists and other scientists to work as lab geeks with extreme qualifications for its research etc and as for engineers, you'd most probably find electrical,materials, mechanical, mechatronic and software engineers at Cern; responsible for designing most of the high tech systems and machinery they use for experimental, research modelling purposes. Engineers actually present at CERN would most probably be there for monitoring and consulting.