You can often see flights with GAF callsign on FR24, so they don't seem to be blocked. It is usually only the newer aircraft (the A340s and A319CJs) though.
No idea who is on board. Merkel is in Berlin, and so is our minister for foreign affairs. This will probably be some other minister, possibly with a business delegation and journalists in tow.
These trips usually pop in the news about a day or two after they happen, I'll let you know here if I see anything in German media.
[Edited 2013-02-15 11:43:03]
Public service announcement: "It's" = "it is". To indicate posession, write "its." Looks wrong, but it's correct grammar