NWA LOA 2008-01: Mesaba Flow Through Agreement (excerpt):
C. Flow Up
1. NWA shall offer employment to MSA Flow Up pilots in priority to any other pilot candidate for hire, with the exception of a pilot who is eligible for Flow Up from Compass Airlines. Offers to MSA pilots to Flow Up will be made in seniority order, provided that , in order to be eligible to Flow-Up a pilot must:
a. Be a Captain, and
b. Have at least thirty (30) months on payroll at MSA, and
c. Meet all objective hiring criteria and requirements as established by Northwest (e.g., total flight time, multi-engine time, PIC, First Class Medical Certificate, passport, FCC Radio permit, ATP certificate) provided such objective criteria shall not be greater or more extensive than the objective criteria for other new hires. A pilot who does not meet these criteria will retain the right to Flow Up at a later date once he is able to meet the criteria referenced above.
This is why XJ pilots must have a degree, or any other "objective criteria".
The Compass flow through language:
3. Compass Airlines pilots will be offered employment at Northwest Airlines before any other Northwest Airlines Affiliate Carrier or new hires from the street directly to Northwest Airlines.
a. Offers to flow up will be in seniority order, provided that, in order to be eligible to flow up a pilot, must:
(1) Be a captain, and
(2) Have at least thirty (30) months on payroll at Compass Airlines (see Sections 7 A. and 14 A.1.c. for definition of "on payroll"; for purposes of this paragraph 22 D.3., a pilot shall be deemed to be on payroll while on military leave).
There is no third line that says anything about meeting any other criteria as the XJ flow does. This is why NWA (and from what I hear DAL) was/is so heavily involved in the hiring process at CP and not XJ. There are only those above two requirements to flow up from CP.