If one cares to spend hours of time googling the words "NdeM C-628" (and any variations thereof), one can confirm the fact that all the native C-628's were indeed scrapped in late 2002 in the Mexico City area.
So, the ex D&H 610 is indeed...the last one standing.
In fact, all the Alcos are gone-save for the corpse of M-630 8611-also said to be found in the Mexico City area.
A very late casualty was the (pretty darn cherry) Ferromex RS-11 501, which was unceremoniously chopped into pieces in a Guadalajara scrapyard. No sign of the engine or other large components.
The prevailing explanation for the wholesale disappearance of the Alcos is this: title to these locomotives was never passed to the various corporate entities that privatized the national system. When enough new power was on hand, the Alcos (along with many old GE's and EMDs) were put up for bid-with NREC and various "partners" being the winner.
Most of these locomotives were salvaged for parts while In Mexico, with the hulks being rendered for scrap locally.