I've been interviewed for a similar role a few years ago now they are looking for a good under standing of the basics electrical, and mechanical engineering , there's alot of equipment you will never have worked on and there will be alot of on the job training make sure you come across as willng and able to do what's needed, they may well ask you what you might do in various emergency situations , you cannot just go switching services off it could cause more problems if operations are being carried out , a knowledge medical gas is a good one to read up on. Planed maintenance on services and equipment will always need authorizing by your superiors and needs to be checked and double checked even locking valves off and displaying the relevant signage whilst work is carried out , permits to work on stuff is not uncommon as is method statements of how and what is expected , they need to know you can think for yourself but never put people or yourself in danger if there's a problem share that problem with your superiors before acting . Best of luck kop