YMCA is absolutely right. It depends on the day. 11-23 is standard for road stages, and 12-25 for climbs. Up front it's a 39/53.
Quote from their (T-Mobile) website:
The shifter
"The new Shimano shifting system also has some changes. Before there was a separate lever for downshifting in addition to the brake lever. Now everything is integrated into the brake lever. It was a little difficult to adjust to at first, but now its like second nature."
The saddle
"The saddle and saddle post have greatly improved. The saddle post now has three drill holes instead of just the one there was in the past. That gives you a lot more possibilities for adjusting the saddle, so you can really put every rider in the perfect position on the bike. For me, that perfect position is at 79.4 cm. I really like the new system."
The bars and stem
"Like last year, Deda will supply these systems. The boys develop new systems every year. There are an unbelievable number of design variations. For normal road races, I use a 140-mm stem with an 82° angle."
The gear system
"Our system allows us to ride 20 gears. In a race, I use 11-23 in back and 39/53 in front. In the highest gear, I can cover 10.5 meters with a single pedal revolution."