[FedCom] USSS Radios Usage Foreign Countries ?

[Ken]

CNN reported that the Bush twins were in Argentina, with an 8 person USSS 
protection team.  Apparently in a restaurant a thief was attempted to or did 
steal one of the twin's purse
http://www.cnn.com/2006/WORLD/americas/11/21/bush.purse/index.html

When the US Secret Service operates in other countries do they operate on 
their same frequencies or others depending upon the country?

Ken