If you are from good University the probability of you getting a job becomes high and vice versa. But if you are from a lower university you may still end up getting good job once you gain experience.  But I have to agree with Pire in one point that  if you study in  top universities particularly in a research base subject, it is most likely that those research are collaborated with some company or for that matter some company might have close link with that university.  The students get hands on experience in attending seminars and conferences and comes across top class employer long before he graduate.  I have seen almost all the student from my department getting a job immediately after graduating because those research are sponsored by big shot companies.