I have two phones, one running 4.4 and one running L. They can both run Qt apps as long as Qt is deployed as part of the APK.
When the L device attempts to install the qml types files, deployment dies. It first reports a failure when attempting to put a file into /data/local/tmp/qt/qml/QtBluetooth/ however, it hasn't even successfully made the directory. I tried creating it manually, but the directory would be removed as part of the deploy step. So it seems that the dir can be removed by the build process, just not created.