Today ModemManager 1.6-rc3 has been released by Aleksander Morgado, the maintainer of the project.
Among the changes, that can be read in the release mail, the good news is that Telit LE910 in QMI composition (PID 0x1201) is working again: in 1.6-rc2 a bug related to port probing prevented LE910 from properly working.
Thanks to Aleksander for fixing this.
ModemManager git repository is available at
git://anongit.freedesktop.org/ModemManager/ModemManager