I noticed that although it is documented, the "amtape update" command is missing. A quick search turned up a patch in a mailing list message: http://marc.theaimsgroup.com/?l=amanda-users&m=114493089503919 I'll attach it; if you like I can send a full diff from the current Fedora CVS tree.
Created attachment 128219 [details] Patch to enable "amtape update"
Amanda 2.5.0p1 is now out, and I'll be building it into Rawhide soon, once my locally built rpms successfully do a nightly backup and a restore.