Those commuting crewmembers are not based out of their home city. That's their domicile. They still start and end their trips at the same base that everyone else works out of (excluding a few airlines that have provisions which allow them to start trips away from base).

It varies from airline to airline, as to what station has the most commuters. At CO, a good number of our commuters come out of Denver since we had a base there several years ago. When we closed our small LA base shortly after 9/11, the number of commuters there went up, etc, etc. There are lots of Florida commuters all over every airline's system for various reasons - a big draw is the lack of state income tax. I can't think of a station in our system where we have no commuters - even int'l cities. I know several that commute from Paris, Rome, London, etc. They're probably on most of your flights, though usually not in uniform.