At least, http://ppewww.ph.gla.ac.uk/~flavell/unicode/unidata07.html shows the standard unicode box. Presumably this is because the syriac fonts are installed in /usr/X11R6/lib/X11/fonts/OTF, which isn't referenced in the fontconfig config file.
Well, sort of. Note that even if the fonts are added, Syriac won't render properly in GNOME (would need a couple of days work within Pango) or probably KDE. (It's conceivable that Qt has support for Syriac, but I doubt it.)
This was fixed in 2.1.2-6 a while ago.