ExpertFlyer does indeed show the MPM for mileage based fares using our Routing Rules function, here is an example of the result:

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Routing Details
Search: Departing YYZ on 10/09/08 for NRT
Fare basis code C7XJEX
Flying AC

MPM FARE - ROUTE NOT APPLICABLE
MAXIMUM PERMITTED MILEAGE IS 7708
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Here is a sample result for a route based fare:

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Routing Details
Search: Departing YYZ on 10/09/08 for NRT
Fare basis code N0M0WCJ
Flying AC

YTO-TYO THU-09OCT08 AC
TAXES/FEES NOT INCLUDED
ADULT FARES
CX FARE FARE C AP MIN/ SEASONS...... MR GI DT
USD BASIS MAX
17 AC 1163.00R N0M0WCJ N | /12M R PA D

SPECIFIED ROUTE: 0301
YTO-YXE/YWG/YQR-YYC/YEA/YYJ-YVR-TYO
YTO-YXE/YWG/YQR-YYC/YEA/YYJ-YVR-OSA(AC/NH/JL)TYO
YTO-YWG-YYC/YEA/YYJ-YVR-TYO
YTO-YWG-YYC/YEA/YYJ-YVR-OSA(AC/NH/JL)TYO
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This is in addition to the Fare Rules.

Hope this helps,
EFV