Switchers
The distinctive GP40TC road switchers were purchased a number of years ago from GO Transit in Toronto. They are extended GP40 carbodies which are mounted on a longer frame, supposedly from an SD40. The extra length, at the rear of the unit, houses an extra power plant that generates head-end power (HEP) for the passenger cars. This would enable GP40TCs to serve as road units on passenger trains, and they have occasionally been used for this purpose, but their main task is usually to move entire trainsets around from station to yard to service facility, and the like.
For example, there is often a GP40TC sitting in Boston's South Station, and it is used to bring in the assembled Lake Shore Limited consist from the yard. Then the road diesels couple to the other end of this consist, if not there already, and depart with it. Vice versa, when a train arrives, it pulls into the station locomotives-first, and the GP40TC can then be used to bring it back out to the yard.
With the delivery of new P42DCs that number up to 207, the GP40TCs had to be renumbered from their original 190-series to the 520-series, which puts them in the same numbering category as the rest of the switchers. They were also re-designated as GP40Hs. However, only a few of them see active service. I myself have seen 520, 522, and 525 recently, which I believe are the former 192, 194, and 197 respectively. Before the renumbering I used to frequently see the 194 performing the switching duties in Boston. The latest news is that the GP40Hs are at Amtrak's Beech Grove shops being rebuilt and will be painted in the latest livery.
Amtrak also has a miscellaneous collection of yard switchers inherited, purchased, or traded from other railroads. They include SW7s, SW-1000s, SW-1500s, MP15ACs, SSB-1200s, CF7s, and several other types. They sport an assortment of paint schemes, from Phase III stripes to yellow-and-blue Santa Fe warbonnets, but the "standard" switcher scheme seems to be a plain silver body with black roof and underframe. Three recently-purchase dunits - an SW-1000 and two SW-1500s - are painted in Amtrak's Phase V livery, similar to the new P42DCs. Most of the switchers are numbered in the 500s, although there are a number of GP38s in the 700 series.