Yeah, probably just two different headends. Comcast is notorious for that.
There use to be several here in Pittsburgh, until they consolidated into three headends.
Before Spring 2007:
22420 - Metro Pittsburgh
22434 - Oakmont/Natrona Hts/New Kensington
22435 - Greensburg/Latrobe
22436 - Leechburg & vicinity
22437 - Coraopolis/Sewickley/PIT Int'l Arpt. area
22438 - Penn Hills
24114 - California/Portvue/Monessen
26163 - Monroeville
26164 - Murrysville-Plum
26165 - Bethel Park/Mt Lebanon/Upper St. Clair
26276 - Freeport area
NOW:
22420 - all of Allegheny, Armstrong, Beaver, Fayette, Greene, Indiana, Washington, Westmoreland counties (except for the headend areas below)
22438 - Penn Hills
26164 - a larger combined area of Murrysville, Plum, Latrobe, Balirsville, and Ligonier