There is another way... still manual though.
I use MapSource to transfer only the maps I need to my Tilt. Unfortunately, as you all probably know by now, Garmin Mobile XT does not allow more than one map on the card simultaneously. If you try to do it from MapSource, the new map overwrites the old map.
So what I do is create mapsets in MapSource and save them for quick recall.
I created a mapset for all of North America using City Navigator 8 maps. Then I transferred that to my Tilt. Next I went onto my Tilt's SD card and renamed the mapset with a "CN-" prefix.
Now, I went back into MapSource and created a mapset for the NW states of the US using my Topographic 2008 maps. Then I transferred that to my Tilt. Next, I went onto my Tilt's SD card and renamed the mapset with a "Topo-" prefix.
Depending upon which mapset I want to use (on road or off road), I just remove the prefix and launch Garmin Mobile XT.
It's a manual process to switch maps, but it's minimal work and they're always on the card where ever I go. I'm sure you could do the same with EU maps or other maps.