The second non-urban or hillside rat in Hong Kong was called Sladen’s Rat in the 1960s with the scientific name of Rattus rattus sladeni. However, it was evident even then that there was something very wrong with the taxonomy and/or identity of the rats in Hong Kong. One of the urban rats is the Black or Roof Rat (Rattus rattus), then assigned to the subspecies flavipectus. This form was thought to be native to southern China but it could, of course, have been a population derived from the native form and others brought in by ship as Hong Kong developed into a massive port from the 1840s.
Whoever said "Fools rush in where angels fear to tread" was surely thinking of rat taxonomy. I am therefore approaching this topic with some trepidation, but also, I hope, more as an unusually brave angel than a complete fool.
Corbet, GB & Hill, JE 1992 The Mammals of the Indomalayan Region: a Systematic Review. Oxford: Oxford University Press.
Chung, K 2003 Hong Kong’s common rat species. Porcupine No 29, August 2003 http://bit.ly/12gkp4A
IUCN - Rattus andamanensis (with bibliography of taxonomy) http://www.iucnredlist.org/details/summary/19361/0