Questions about recruiting/employee referrals

For those of you who work or have worked in IB or have been involved in IB recruiting, I am curious about the following:

1) How helpful is it to have someone (analyst) forward your resume along to HR? Particularly interested in schools with OCR.

2) How do referral systems vary at the different banks?

3) Would it beneficial to have them forward these resumes now or later, as recruiting for summer recruiting gets closer?

4) Do recent summer interns and new analysts have any leverage in recruiting? Can they send resumes/give interviews to people?

Know some of this information is scattered around and perhaps outdated. Thanks for your insights in advance.