The weekly updated img files on http://garmin.na1400.info/routable.php now contain transliterations for 21 Areas:
albania, belarus, bulgarije, cyprus-turkish, czech-republic, estonia, georgia, greece, hungary, kaliningrad, latvia, lithuania, macedonia, moldavie, poland, romania, russia, serbia, slowakia, turkey and ukraina. Attentioen only 's with a valid place AND a name tag are transliterated when needed. (valid place |town|city|suburb|village|hamlet|).

So for instance in greece
http://api.openstreetmap.org/api/0.6/node/83945071




will show up in your garmin as " Agios Nikolaos (Agios Nikolaos). While
http://api.openstreetmap.org/api/0.6/node/83943762



will show up as “??? ??? (Agios Andreas)” because it is an island.

I now understand that such a restriction is unwanted. In the next update translit will handle all nodes with a name tag.