I don't think anyone would ever think of making this a standard for all lines. It isn't so much a historical nod as being as natural as breathing in these parts.
Metro was all under one municipal transit system. and Metro was for all intents and purposes a single city with a single regional downtown and a smooth growth continuum from said downtown.
I almost wonder why Mississauga wasn't named Port Credit instead. PC is big enough and centrally located enough for it. Certainly more so than Markham Village is for Markham.