Are ALL keg beer non-pasteurized? I understand bottles or cans may or may not be pasteurized. How about Keg beer? I was under the impression that all keg beers are not pasteurized because of the volume, is that true? Are there exceptions?
Beer kegged in the USA is usually stored cold and consumed quickly. Therefore, sterile filtration is all that's needed. To make it stable in a wider variety of temperatures, especially shipping it over an ocean, they pasteurize it.

From Pasteurized Kegged Beer: 


  Non-Pasteurized
  
  For the most part keg beer brewed and packaged in kegs in the U.S. is
  not pasteurized. During the packaging process non-pasteurized draft
  beers are sterile filtered and chilled to the point that any surviving
  bacteria, which could ferment the beer, become dormant. Kegs are kept
  cold ( &lt; 50° F ) from the brewery to the point of dispense. Draft beer
  dispensed from a keg should be fresh by storing as short as possible,
  and serving cold at 38° F.
  
  Temperatures above 38° F may promote non pasteurized draft beers to
  turn sour or cloudy. Should the temperature rise above 50° F, the
  dormant bacteria which ferments and spoils beer will once again become
  active and, subsequent growth will rapidly begin to spoil flavor and
  cloud the beer.
  
  Pasteurized
  
  Most of the keg beer brewed and packaged outside the U.S. (Import
  beers), are heat pasteurized during packaging. This process kills off
  the bacteria that ferment and spoils the beer.
  
  Pasteurized draft beer kegs can be transported and stored at room
  temperature. The beer in these kegs can be flash cooled at the point
  of dispense. However, most imported kegs are stored and dispensed at
  the same temperature (38° F) as domestic, non-pasteurized kegs.