I haven't tried that beer but I happen to be brewing an Alt (a Northern German Alt) this weekend so I can comment on what I've learned about Alts in general. Many german beers have very simple grain bills. Mine will be mostly German Light Munich malt with a small amount of Carafa Special II (about 2%) and Carafoam (about 5%). I might add a tiny amount of Caramunich but probably not (see below).
According to Daniel's Designing Great Beers
; caramel/crystal malts are not really appropriate but acceptable in small quantities. No hops should be added 30 min or less remaining in boil (just a bittering addition, Spalt if you can but any German noble will do). Attenuate highly, like in the 77%-80% ballpark. I'm using Wyeast 1338 European Ale yeast
which has low attenuation numbers on the Wyeast site but I've gotten way higher attenuation than those numbers and they say it's a good yeast for Alt.
Hope that helps and good luck!