Please ... it will be binary format. Even the government isn't so wasteful to transmit data as xml. And if it did you could easily find where the servers were located by the 5 nuclear power plants needed to power such parsing.
HUR DUR XML IS BAD HUR DUR
No, JSON.
I hate to tell you this, but the government has never been concerned enough with overhead to not use something like XML. Frankly its probably tab deliminated ASCII.
We'd be lucky to see a binary protocol.