VERIFIED SOLUTION i

How to find out how MailStream Plus verifies discounts based on the entry point/locale key for each facility

On each xxx PT entry point parameter(s) in a job (ENT PT, ADC PT, NDC PT, SCF PT) it can be indicated the type(s) of entry discount the pieces are eligible for, using positions 58 (DADC), 60 (DSCF) and 61 (DNDC).  (Position 59 is for DDU entry.)
 
As appropriate based on the pieces being in the proper container levels and destination, MailStream Plus (MSP) will then give the pieces the Destination discount(s) the entry point parameter has indicated on it. 

There is no validation made as to the physical entry point being suitable for the discount. 
By indicating the mailing is eligible for the discounts via positions 58, 60, 61, MSP expects that the pieces are going to be entered at the correct entry location(s) where they are eligible for the discount. (i.e. The correct entry facility as required by the USPS presort regulations).
 
Mailers must be careful to only select the Destination discount (or discounts) the mailing is eligible for, based on the facility(ies) where the mail will be entered.
 
--------EXAMPLE BELOW -------------------------------------
 
There are a lot of possible variations in mailings, but here is one example to show how it worked.  Say an ENT PT for a Standard Mail letter mailing looks like this-
ENT PT               22401 Virginia                        YY  O
....+....1....+....2....+....3....+....4....+....5....+....6....+....7....+
In this example, position 60=Y says the mail is eligible for SCF discount, *and* position 61=Y means the mail is eligible for the NDC discount. 
With both of the discounts selected, it indicates that some mail pieces will be entered where required as needed for DSCF, and other mail pieces will be entered where required as needed for DNDC rates. 
MSP will perform the presort so that the mail pieces that are eligible for the DSCF discount will get it, and then mail pieces that are eligible for the DNDC discount will get it. 
Note- if the SCF and NDC are not located at the same facility, then some mail will be transported to and entered at the USPS SCF facility, and some will be transported to and entered at the USPS NDC facility.
 
For users interested in the Mail.dat files-
Since position 64 is an O (for Origin facility type), CSM-1106 (Entry Facility Type) will get an O, and CSM-1167 will get “ORIGIN”.
But because of the discounts requested in position 60 and 61, CQT-1105 (Destination Entry) will have a ‘B’ (for DNDC) for some records, and an ‘S’ (for DSCF) for other records.  
UPDATED:  August 11, 2017