Hi,
I did not know you could patch Basecamp.
But anyway .db file should work on not patched Basecamp.
I downloaded the two versions (image and Mapsource) of Topo Germany Pro 2012 which is very similar to Topo Transalpine (new active routing with .db file as well).
I put the .img file with .db file in Garmin folder on a SD card, then read this card in Basecamp : when I created a route, no choice of trail was proposed.
But when I created a route in Basecamp with Mapsource version installed on my PC, choice of trail was proposed.
In conclusion, .db file only works in Basecamp with Mapsource version and not with .img version !