Sorry, I’m joining this a bit late.
HSR Fan -until 1991 dual power Amtrak Empire service equipment had underrunning shoes for GCT. Then as RedSox suggests they were summarily changed to overrunning for NYP. In both eras I would think they had to be retractable to get past MN’s clearance protection blocks north of Croton. The P32AC-DM’s are, but I’m not sure the FL9 picts show that type of shoe so maybe the blocks were removed for a while. For ShadyJay’s point, one off visits to GCT since 1991 may have just cheated a bit and used the diesel.
Jim Boylan -half of the reason for creating the EP2 was to have enough power to get up the East River tunnel grades, the other half was to get up the HG bridge grades, both far steeper than anywhere else in NH electric territory. And they were given retractable overrunning shoes for DC operation. But despite spending the money to create the locomotives it appears they never actually ran west of Sunnyside SS-2 at Woodside Ave until 1933. I wonder if having taken care of NH’ s steam delivered trains from 1917, PT&T’s union objected to letting NH crews run through when the electrics became available in 1918, or could it be that the schedules were so sparse that the EP2s would have had to be constantly deadheaded all the way back to Oak Point? In the AC era the engines just laid over in a corner of NYP.
Drewh -1. although as Noel says the FL9 convertible shoes successfully hauled trains to both stations there have also been past conversations of long term trouble. 2. extending to Albany would never save enough fuel to justify the huge cost. 3. over 10-20 miles only the higher voltage of catenary is economic for new work, closer than that we just don’t have many samples in the world with which to compare 3rd rail and cat costs. You would have to count in closer 600v substation spacing, differences in AC/DC loco costs and bias that by any need for MUs. 4. the FL9s operated under AC catenary but never used it. Triple power ideas like this have been proposed but they never seem to be by anyone with practical knowledge.
Bill