I guess the most basic way of saying it is that the BMP turns pledging into a college-long education process. There are three main steps that all brothers MUST do to be eligilbe to become alumni, then two other advanced educational steps that are optional for those that want to continue. There is also an increased emphasis on older members mentoring younger members.
For more information, check out this link:
http://sigep.org/documents/bmp-cliff-notes.pdf
~Benson