Reichstag Attack Uncovered?

Der Spiegel reports that al Qaeda is planning an attack on Berlin’s Reichstag. Information on the plot comes from a tip received by a man who wanted to leave the terrorist organization:

According to information obtained by German security authorities, al-Qaida and associated groups are believed to be planning an attack on the Reichstag building in Berlin, the headquarters of Germany’s parliament and also an attraction visited by thousands of tourists every day. As part of the attack, terrorists would seek to take hostages and perpetrate a bloodbath using firearms. …
According to the caller, the terror cell is comprised of six people — two of whom are believed already to have traveled to Berlin six to eight weeks ago, and are now staying in the city. Four other perpetrators — a German, a Turk, a North African and a further man the jihadist could not identify — are currently waiting to travel to Germany. The attacks are purportedly being planned for February or March.

Der Spiegel says that additional information came from the FBI, which alerted German authorities to an al Qaeda plan to use Shia Muslims from India to carry out an attack in Germany. From the magazine’s account–which also notes that the CIA is reportedly skeptical about the intelligence–it does not appear that any of the alleged plotters are in custody.