I suppose, but I don't think so. That's why the Airports/Time Capsules don't have an ADSL modem built in or available as extra, it's so much easier to produce one product that can be marketed globally without any regional variations.
As Feek Says I dont think so either..... It be good if Apple could build in a modem on their airport then everything is in one package rather than stacking a Modem with it. But that apple