To fill in a couple of blanks for people who didn't find the original coverage, the "FL9" solution is very time-limited, only for the expected duration of the planned Empire Connector shutdown to repair Sandy damage to the Spuyten Duyvil bridge - perhaps 3 to 6 months even with New York contract feather bedding? - and is floated only because nose-door escape access is needed in parts of the Park Avenue tunnels to GCT. The cab-car 'alternative' was mentioned for the same reason.
It is interesting to consider what might be done to the CDOT units to fit them for operation as remote cabs instead of pushers. I do not know if the two 'blue-carded' units can operate reliably with their prime movers shut down as I do not think restoring the third-rail shoe system is a very good solution and these units may not have a full set of trainline connectors for current equipment (with a DM on the west end).