Browse another encrypted time machine backup that's on a NAS
If OS X detects the NAS as a possible backup destination, you should be able to option-right-click (hold option while right-clicking) the Time Machine icon in the menu bar, and select "Browse Other Backup Disks". The AFP mount should show up there and you should be able to browse it.

Alternately, just mount the sparsebundle. It works just like a .dmg. If double-clicking doesn't give you the option to type in the password and mount it, you can drag it into Disk Utility and mount it from there.