When using icu4c built as archives, link lines need to include the data library to resolve all symbol references. The two cases so far are in icu/icu.pro and tools/tools.pri:
qt-everywhere-opensource-src-5.2.1/qtbase/config.tests/unix/icu/icu.pro: LIBS += -licui18n -licuuc -licudata
qt-everywhere-opensource-src-5.2.1/qtbase/src/corelib/tools/tools.pri: LIBS_PRIVATE += -licui18n -licuuc -licudata
With shared libraries, library dependencies will solve the resolution problem. Archives need this to be explicit to pick up the data. It may be that other ICU build/package styles will have problems with this so it may need to be looked at more carefully.