1) One CANNOT compare the way locomotives are maintained on a heavy haul rail operation vs a "conventional" loose car railroading operation.I don't have much to add on the C-636's intrinsic quality, but I'm not sure its history supports very strong claims for it.
The type lasted a long time on the Canadian railroads and on captive iron-ore railroads in Quebec and Western Australia (actually the M-636 on the former). But
(i) EVERYTHING lasted a long time in Canada. In the early 1990s CN and CP had older locomotives, on average, than any of the major U.S. railroads. I think this had more to do with Canadian tax laws than with the quality of the locomotives inquestion!
(ii) The iron ore carriers were also railroads of a type that one would expect to keep whatever locomotives they had for a long time: small, fairly uniform, fleet of locomotives and a shop that knew them well.
As for the C-636. The Australian operators apparently thought the Alco-design "Hi-Ad" truck was good for their railroads (heavily engineered, good track, no excessive curvature): they liked it better than they did the MLW ("Dofasco") truck on the M-636. In the 1980s, they started to replace the C-636 fleet by having them re-built (by Goninan, GE's Australian licensee) as C36-7 or C40-8 from the frame up, keeping the Alco trucks but getting rid of the aging Alco engines. Few if any of their M-636 were rebuilt in this manner.
The Cartier, BHP, etc. is nothing more than a giant conveyor belt, an element of a huge process plant. That element has to be absolutely reliable (theoretically 100 percent), in order to avoid costly shutdowns of the entire operation.
Ergo, the maintenance standards for locomotives (and cars and signals...) are much more rigorous than any Class One rail outfit.
By extension, the C/M-636's used in this service received many upgrades that the Class One rail operations didn't even bother with. They just choose to retire the locomotives on account 'minority' status. This is why the ex-Cartier units are still performing revenue service for a new owner.
2) Canada faced many of the same regulatory issues as the American railroads did pre-Staggers...with accompanying shortage and cost issues relating to 'new' capital. Lack of capital=lack of new locomotives. With that in mind, I still the Canadian railroads maintained their locomotives in a superior fashion to the American roads.
Today, the Canadian roads long ago underwent regulatory reform-witness the sheer number of line spin offs and new operators.
3) The primary suspension of the Alco Hi-Ad truck (coil springs) is much more compliant than the steel/elastomeric sandwichs used on the MLW Hi-Ad truck. In other words, Alco truck does a superior job of not transmitting lateral forces down to the track structure. Rides better, too.