Is it true that when you near the completion of your program, that companies / employers pick out the students with the highest marks and offer them jobs, or do you have to do the job searching after you graduate?

You still have to apply... if you don't apply, employers will not know about you and your chances of getting a job is ~0%

High marks will probably get you the interview, but your knowledge and people-skills is what will get you the job.

The University cannot release people's marks to employers, that violates privacy rules in a huge way. They can release general stats about the program I think, but no way could they tell employers where students rank/what their grades are.

The only way a potential employer will know your grades is if you tell them (or if you get Provost Honour Roll I guess, they'll know you got all 12's that term). So no, there is no behind-the-scenes "scouting" of students.

Employers don't really care about grades. They want to see the skills you can bring to the table. By looking at your name it seems like you're interested in MedRad, so employers are going to want to see how you suceded in your clinical placements, they'll most likely ask your field instructors for references. I would suggest meeting people in the field and developing good relationships in the program, however that doesn't mean it's an excuse to slack off. In order to succeed in clinicals you'll have to succeed in clases, you may be asked in interviews about the knowledge you have learned in classes and how you would apply it to various scenarios.

tl;dr, employers would rarely ask to see a transcript, but you still gotta do good in your coursework and jazz.

Some jobs require the grades since they want the cream of the crop. All of them for sure are looking for work experience (most important) and also stuff you have done to show skill development in your extracurriculars/community involvement

Grades are more or less very important in the actual application process. During the interview, it's more about yourself/experiences. But, resume experience will be weighted more heavily than grades, for sure.