The device have Bluetooth 4.0 support and that include LE, but the current APIs provided are old and does not properly support LE. Bluez needs to be updated to 5.x and proper BTLE Qt APIs should be added.
Edit by c.la 20150413: I just noticed in Harbour the app Parrot ZIK 2.0 Manager that includes a backport of QtBluetooth 5.4. Can't this be included in jolla update?
EDIT 2015-12-15 by c.la: this topic will be discussed on Dec, 17th Jolla Community meeting. If you plan to attend please edit the post and add your name in the list of substitutes in case I can't show up (50% chance atm)