I think this is a good thing. The Expos are not a team anymore, but they were at one point, and the HOF is about both achievement and history.
The Expos were always my second favorite team as a youngster and I went to a number of games in Montreal. For a relatively obscure franchise, a number of very good players played there, including Gary Carter, Tim Raines, Dennis Martinez, Andres Galaraga, Larry Walker, Moises Alou, John Wettland, Randy Johnson, Pedro Martinez and Vlad Guerrero.
Having them represented a bit in the Hall honors the fact that they were a team in Major League Baseball for 35 years. Interestingly they were the Expos for 10 years longer (1969-2004) than the "Dodgers" were Brooklyn's team (1932-1957). Of course the Dodgers were more influential.