In theory, the employer should continue interviewing candidates as the LMIA is just an alternative if an employer can't find any qualified Canadian worker. However, I don't believe that anyone who is applying for a LMIA is going to keep interviewing people after the application is submitted.
If there are any missing documents, they will send a notification asking for additional documents. Once they have all the documents, they will evaluate them and call your employer. I don't know which kind of question they ask, but usually it takes around 30 min to 1 hour. The decision comes after the call - usually it takes one or two days, but I've seen cases that took a month. When it comes to LMIA, there isn't any standard.
The time that takes to get the call is another thing that has no pattern. It can take 2 weeks or 4 months. Nobody knows and the only thing they will tell you if you call is that it is being processed (very frustrating).