Callaway,
MDA transformed over the course of several concessionary agreements, from initially a 4th wholely owned Express carrier (4th at that time) to disappearing completely. Initially, it would fly all RJ's over 50 seats and be staffed 1st with furloughed mainline pilots, 2nd with pilots at the other 3 wholely owned Express carriers, then 3rd with off the street hiring for any remaining vacancies (which never happened). Before startup, the company made the decision to operate MDA on the mainlime certificate althouogh it was a separate corporate entity. Later concessions, approved by the "real" mainline pilots allowed bigger RJ's to be farmed out so MDA ended up just operating the E170's. A further concession, again voted on by the "real" mainline pilots allowed the E170's to be operated by contract carriers which set the stage for Republic buying the E170's. Finely, MDA was merged with US Inc (mainline) so disappeared as a separate corporate entity - oldie knows so much about it I'll let him tell you when that happened.
So as far as a legitimate reason for considering the MDA folks furloughed was that 1 - that was what was initially negotiated, and 2 - it was a separate corporate entity from mainline although operating on the mainline certificate, and 3 - the pilots had a completely separate contract (also as initially negotiated). There are several more twists and turns in the MDA saga, but that's the gist of it.
As for why they should have been considered active mainline pilots, one can argue that operating on the mainline certificate should have been the test, or getting paychecks from the same account as mainline, or several other points. But when the corporate entity that was MDA was merged into mainline (US Inc) it became impossible to argue that MDA pilots weren't mainline pilots. That didn't keep the MEC and company from showing the MDA pilots as furloughed, however it is what allowed Jerry Glass to testify that MDA didn't exist in the change of control arbitration.
Jim